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HEREDITY,  DISEASE  AND 
HUMAN  EVOLUTION 


HEREDITY,  DISEASE 

AND 

HUMAN  EVOLUTION 


BY 

Prof.  Dr.  Med.  HUGO  RIBBERT 

Professor  of  Pathology  at  the 
University  op  Bonn 


TRANSLATED  FROM  THE  GERMAN 

BY 

EDEN  AND  CEDAR  PAUL 


1918 

THE  CRITIC  AND  GUIDE  COMPANY 

12  MT.  MORRIS  PARK  WEST 

NEW  YORK 


BIOLOGY 
LIBRARY 


Copyright,  1918, 
By  The  Critic  and  Guide  Company 


CONTENTS 

CHAPTER  PAGE 

I.   Preliminary  Considerations 9 

II.   The  Frequency  of  Diseases  and  the  Limits 

OF  Health 19 

III.  Do  Normal  Human  Beings  Exist?       ...       29 

IV.  The  Significance  of  Diseases  to  Individual 

Men  and  in  Relation  to  the  Freedom  of 
THE  Will 44 

V.   The  Significance  of  Diseases  to  Society     .       54 

VI.   The  Significance  of  Diseases  to  the  Off- 
spring        64 

A.  Injuries  In-flicted  upon  Children  by  Bad 
Upbringing  and  Education      ....       64 

B.  Appearance  of  Diseases  in  the  Offspring. 
Heredity 68 

1.  General  Phenomena  of  Heredity  ...       75 

2.  Principles  of  Inheritance 94 

3.  Occurrence  in  the  Offspring  of  Qualities 
Acquired  by  the  Parents  (Inheritance  of 
Acquired  Characters) 106 

4.  Diseases  Affecting  the  Parents  and  Re- 
curring in  the  Children  ("Hereditary" 
Diseases) 124 

5.  Rules  in  Accordance  with  which  Diseases 
Affecting  the  Parents  Make  Their  Ap- 
pearance in  the  Children 136 

6.  Genesis  of "  Hereditary "  Diseases       .     .     150 

V 


,)^4  \Uh} 


vi  CONTENTS 

CHAPTER  PAGE 

7.  Increase  in  "Hereditary"  Diseases.     .  169 

8.  Is  the  Human  Race  Degenerating?  .      .  181 

VII.   Can    Disease    Favour    Human    Evolution? 

Teleology 185 

viii.   d  sease  and  religion 202 

IX.   The  Abolition  of  Disease.    Racial  Hygiene  218 

X.  How  Shall  We  Come  TO  Terms  WITH  Disease?  230 


HEREDITY,   DISEASE   AND 
HUMAN    EVOLUTION 


CHAPTER  I 

PRELIMINARY  CONSIDERATIONS 

A  KNOWLEDGE  of  the  leading  peculiarities  of  disease  is 
evidently  an  essential  preliminary  to  the  consideration  of 
the  significance  of  diseases  in  the  process  of  human  evo- 
lution. One  who  wishes  to  speak  of  disease  must  know 
what  it  is.  But  we  do  not  need,  for  such  an  exposition, 
the  strictly  scientific  groundwork  of  knowledge  possessed 
by  the  pathological  expert.  It  will  suffice  to  start  with  a 
clear  definition  as  to  the  essential  nature  of  disease,  one 
which  will  give  us  a  general  understanding  of  the  influence 
of  this  process  upon  the  bodily  and  mental  capacity  of 
the  individual  human  being,  and  in  association  therewith 
upon  the  race  as  a  whole. 

What,  then,  is  disease?  The  answer  to  this  question  is 
so  easy,  that  it  might  seem  almost  needless  to  give  an 
answer  at  all.  For  to  every  one  who  approaches  the  ques- 
tion with  an  open  mind  it  must  be  obvious  at  the  first 
glance  that  disease  invariably  implies  an  injury  to  the 
patient,  in  consequence  of  which  his  functional  capacity 
is  always  impaired.  Whether  the  disease  is  one  primarily 
affecting  a  single  organ  merely,  or  whether  the  whole  body 
is  sjrmpathetically  concerned,  there  results  in  every  case 
a  depression  of  some  bodily  or  mental  function,  or  of  both 
bodily  and  mental  functions  combined.  Consequently  a 
diminution  in  the  functional  capacity  of  a  single  organ,  of 

9 


10  Heredity,  Disease  and  Human  Evolution 

several  organs,  or  of  all  the  organs  of  the  body,  is  the 
characteristic  indication  of  disease.  Disease  is  the  sum-total 
of  the  depression  in  the  bodily  and  mental  functions. 

This  disturbance  in  the  functional  activity  of  the  organs 
is  not  something  existing  by  itself,  for  it  must  obviously 
be  associated  with  the  individual  organs;  and  just  as  nor- 
mal function  depends  upon  the  normal  structure  of  the 
parts,  so  dimijiution  of  function  arises  from  changes  in 
the  structure  or  composition  of  the  tissues.  These  changes, 
in  turn,  are  conditioned  by  injurious  influences  of  the 
environment,  such  as  heat,  cold,  abnormal  nutritive  condi- 
tions, hunger,  poisons,  micro-organisms,  etc.  When  such 
influences  affect  the  organs,  these  are  unable  to  resist  them ; 
the  organs  are  burned,  frozen,  undergo  chemical  changes, 
and  so  on.  In  this  way  there  result  alterations  of  extraor- 
dinary complexity,  greatly  diversified  according  to  the 
regions  in  which  they  occur.  The  noxious  influences  affect 
now  one  portion  of  the  body  and  now  another,  inducing 
abnormal  states  with  which  even  those  without  medical  ex- 
perience are  familiar  when  the  superficial  portions  of  the 
body  are  involved.  The  layman  knows  external  injuries 
of  various  kinds;  burns,  for  instance,  since  these  are  so 
common ;  boils ;  ulcers,  such  as  often  occur  on  the  legs ;  such 
tumours  as  cancer,  etc.  None  of  these  changes  are  com- 
patible with  the  normal  working  of  the  affected  parts.  It 
is  obvious  that  an  organ  injured  by  any  of  the  influences 
that  have  been  enumerated  cannot  continue  to  do  its  work 
as  well  as  before.  Hence  arises  disease.  The  definition 
previously  given  may  therefore  be  somewhat  amplified,  as 
follows:  disease  is  the  sum-total  of  the  depressions  in  the 
functions  of  our  organs  which  result  from  alterations  in 
the  structure  of  the  parts.  This  definition  appears  self- 
evident  to  such  a  degree  that  the  reader  may  be  astonished 
to  learn  that  formerly  many  men  of  science  were  disposed, 
as  are  not  a  few  still  disposed  to-day,  to  explain  disease 
as  an  increase  in  the  vital  processes  of  the  body.  This 
view  will  be  discussed  in  some  detail,  because  its  exposition 


Preliminary  Conside>;cations  11 

will  render  even  plainer  than  before  the  nature  of  disease 
as  a  depression  of  functional  processes. 

How  did  the  converse  view  come  into  existence  ?  One  of 
its  leading  advocates  was  Paracelsus,  the  celebrated  physi- 
cian who  flourished  in  the  first  half  of  the  sixteenth  cen- 
tury. He  was  bom  at  Einsiedeln  in  Switzerland,  lived 
for  a  time  at  Basle,  and  subsequently  practised  his  profes- 
sion in  Germany  and  other  countries.  He  died  in  the 
year  1541.  Paracelsus  described  disease  as  an  independent 
entity,  invading  the  human  body  from  without,  from  the 
earth,  the  air,  or  the  stars,  taking  up  its  life  in  the  body, 
and  there  inducing  disturbances.  Thus  he  held  that  the 
disease  lived  its  own  life  in  the  body.  In  another  form 
this  conception  dates  from  an  earlier  age.  In  the  neo- 
platonism  of  Alexandria  the  notion  of  the  independent  na- 
ture of  disease  plays  a  great  part  in  the  form  of  the 
daimons,  those  spiritual  beings  intermediate  between  angel 
and  man,  by  whose  entrance  into  the  body  mental  disor- 
ders, in  particular,  were  supposed  to  be  caused.  These 
daimons  were  considered  to  live  on  independently  in  the 
host.  This  naturally  involved  the  idea  that  they  might 
leave  the  sick  man,  or  might  be  forcibly  expelled  from 
his  body.  This  erroneous  notion  has  persisted  for  fully 
two  thousand  years,  even  if  to-day  it  is  found  only  in 
comparatively  uncivilised  regions.  Even  now  we  occasion- 
ally come  across  persons  who  believe  themselves  to  be  pos- 
sessed; and,  yet  more  astonishing,  we  are  still  occasionally 
horrified  to  learn  that  priests  have  had  recourse  to  the 
practice  of  exorcism. 

As  far  as  science  and  the  cultured  section  of  humanity 
is  concerned,  such  views  have  long  been  abandoned.  We 
now  know  that  diseases  are  not  independent  entities,  but 
that  they  are  induced  by  changes  in  our  own  organs.  What 
happens  is  not  that  the  disease  exists  first  and  gives  rise 
to  disturbances  in  the  organs.  The  primary  stage  is  the 
occurrence  of  various  changes  in  the  organs  incompatible 
with  the  normal  functioning  of  these,  and  the  functions 


12  Heredity,  Disease  and  Human  Evolution 

are  therefore  impaired  or  suspended.  The  brain  of  a 
lunatic  is  a  brain  that  has  undergone  changes,  and  these 
changes  are  the  cause  of  the  mental  disorder.  Abnormal 
changes  take  place  in  the  valves  of  the  heart,  and  these 
give  rise  to  serious  disorders  in  the  circulation  of  the 
blood.  In  the  person  suffering  from  tubercle,  extensive 
changes  have  occurred  in  various  organs,  and  especially 
in  the  lungs,  impairing  the  function  of  breathing  until  ulti- 
mately this  can  no  longer  be  performed.  The  breaking  of 
a  bone  necessarily  gives  rise  to  an  impairment  or  to  the 
complete  loss  of  the  power  of  movement  in  the  affected 
limb.  Thus  we  see  that  disease  is  no  independent  entity, 
but,  on  the  contrary,  that  the  phenomena  of  disease  in  the 
living  body  depend  upon  the  occurrence  of  changes  in  the 
organs  of  the  body. 

This  applies  to  disturbances  of  the  mind  just  as  much 
as  to  disturbances  of  the  body.  Function  per  se  can  never 
become  abnormal.  Alike  in  the  normal  and  in  the  patho- 
logical state,  function  is  inseparably  associated  with  some 
organ  of  which  it  is  the  function;  it  does  not  float  in  the 
air,  it  is  not  independent.  Abnormalities  of  function  can 
arise  only  in  connexion  with  abnormal  changes  in  the 
organ.  In  the  case  of  the  nervous  system,  and  as  regards 
certain  mental  disorders,  it  is  true  that  we  are  accustomed 
to  speak  of  purely  functional  disorders  without  reference 
to  any  associated  anatomical  changes.  All  that  this  means, 
or  all  that  it  ought  to  mean,  is  that,  in  the  cases  in  ques- 
tion, we  have  not  yet  been  able  to  discover  any  charac- 
teristic changes  in  brain  and  spinal  cord.  No  one  who 
is  a  serious  student  of  the  question  doubts  that  in  these 
cases  also  there  are  anomalies  in  the  structure  of  the 
nervous  system  upon  which  the  observed  mental  disturb- 
ances are  dependent;  but  these  changes  are  often  of  so 
minute  a  character  that  it  is  difficult  to  demonstrate 
their  existence  even  with  the  aid  of  the  microscope. 

Anatomical  changes  underlie  all  diseases,  whether  they 
are  spoken  of  as  functional  or  not.    These  changes,  in  their 


Preliminary  Considerations  13 

turn,  do  not  arise  spontaneously.  As  we  have  already 
shown,  they  are  evoked  by  noxious  influences  which  affect 
the  organism  and  cause  changes  in  its  parts.  The  neo- 
platonists  and  Paracelsus  may  be  said,  in  a  strictly  literal 
sense,  to  have  attained  long  ago  to  this  view,  even  though 
their  expression  of  the  idea  was  an  altogether  indefinite 
one.  The  conviction  was  forced  upon  them  that,  especially 
in  the  case  of  diseases  of  sudden  onset,  something  must 
have  entered  the  organism  from  without,  but  they  did 
not  know  as  yet  what  this  something  was,  and  they  were 
therefore  led  to  assume  the  existence  of  independent  dis- 
ease-entities, to  which  they  gave  fantastic  lineaments.  At 
that  date  the  error  was  of  little  consequence.  The  inner 
structure  of  the  diseased  body  was  unknown;  little  or 
nothing  was  known  as  to  its  differences  from  the  healthy 
body;  it  could  not  occur  to  any  one  to  make  morbid 
phenomena  dependent  upon  changes  in  the  organs.  Not 
until  after  the  death  of  Paracelsus  did  a  knowledge  of 
organic  changes  gradually  begin  to  develop,  and  more  than 
two  centuries  elapsed  before  the  Italian,  Morgagni,  in  the 
year  1761,  definitely  referred  diseases  to  anatomical  altera- 
tions. In  his  famous  book,  De  sedihus  et  causis  morborum 
per  anatomen  indagatis,  he  showed  that  phenomena  ob- 
served during  life  correspond  to  definite  changes  in  the 
organs. 

Among  the  ancients,  even  in  the  absence  of  knowledge 
of  anatomical  conditions,  sounder  views  had  prevailed. 
Four  hundred  years  before  the  Christian  era,  Hippocrates 
referred  diseases  to  a  change  in  the  body,  to  an  abnormal 
composition  or  admixture  of  the  bodily  fluids.  In  the 
second  century  of  our  era,  the  celebrated  Roman  physician 
Galen  adopted  like  views,  and  on  the  strength  of  his  au- 
thority, they  persisted,  though  somewhat  modified,  into 
recent  times.  The  doctrine  in  question  is  known  by  the 
name  of  the  humoral  pathology,  since  in  this  view  the 
essential  changes  concern  the  juices  or  humours  of  the 
body.     Other  physicians  of  ancient  times  regarded  dis- 


14  Heredity,  Disease  and  Human  Evolution 

eases  as  dependent  upon  changes  in  the  fixed  parts,  upon  a 
condensation  or  rarefaction  of  their  structure,  and  this 
theory  has  been  termed  the  solidary  pathology.  The  views 
in  question  were  necessarily  incomplete,  but  they  were 
much  nearer  to  the  truth  than  speculations  about  daimons 
and  independent  disease-entities.  We  need  not  further 
consider  the  humoral  and  the  solidary  pathology.  We 
are  rather  concerned  with  the  fantastic  notions  of  daimons 
and  of  special  disease-entities,  inasmuch  as  we  wish  to 
show  how  it  came  about  that  diseases  were  regarded  as 
manifesting  an  increase  in  the  vital  processes.  The  con- 
nexion is  not  difficult  to  find.  It  was  supposed  that  the 
invading  entities  would  themselves  develop  greater  vitality 
in  the  affected  organism,  and  that  a  further  consequence  of 
this  would  be  to  stimulate  the  organs  to  increased  vital 
activity.  These  ideas  were  especially  applicable  to  those 
suffering  from  mental  disorder,  for  in  such  persons  there 
can  often  be  observed  a  remarkable  excitability,  and  an 
apparently  enormous  increase  in  functional  capacity,  so 
that  it  might  well  be  supposed  that  the  daimons  were  espe- 
cially active.  More  careful  consideration  would,  however, 
have  led  to  the  reflection  that  it  was  impossible  for  these 
foreign  entities,  of  necessity  injurious  to  the  organism, 
to  arouse  therein  a  more  exalted  life.  But  the  argument 
was  not  pursued  so  far.  Attention  was  concentrated  upon 
the  disease-entities  that  had  invaded  the  body  and  con- 
tinued to  live  there. 

These  discarded  views  lead  us  to  conceptions  of  our  own 
day,  which,  though  greatly  modified  to  correspond  with 
modern  ideas,  nevertheless  return  to  some  extent  to  this 
notion  of  the  independence  of  diseases.  When  microorgan- 
isms were  first  discovered,  there  was  a  tendency  at  the 
outset  to  regard  them,  not  as  noxious  influences  which  give 
rise  to  changes  in  the  body,  but  as  disease-entities  for 
which  the  organism  serves  as  a  habitat  and  the  effect  of 
whose  vigorous  proliferation  is  to  arouse  in  that  organism 
an  enhanced  vital  activity.    The  microorganisms  were  to  a 


Preliminary  Considerations  15 

larg'e  extent  identified  with  the  disease,  in  the  belief  that 
when  the  presence  of  the  former  was  established,  the  exist- 
ence of  the  latter  could  be  assumed  without  further  in- 
quiry. Since  microorganisms  are  characterised  by  vigorous 
proliferation  it  was  considered  a  natural  inference  that  the 
disease  associated  with  their  presence  must  be  regarded  as 
a  condition  of  enhanced  vital  activity.  At  the  present 
day  the  correct  view  of  the  matter  is  generally  understood. 
Microorganisms  are  mere  noxious  disease-producers,  just 
like  poison,  heat,  ete.  Their  presence  induces  changes  in 
the  organs,  and  these  changes  give  rise  to  disease  through 
the  depression  of  function  that  ensues. 

The  notion  that  diseases  might  signify  an  intensification 
of  the  vital  processes  was,  however,  not  derived  solely  from 
the  conception  of  disease-entities  and  micro-organisms  in- 
vading the  living  body  from  without.  It  was  held  that 
from  the  behaviour  of  the  parts  of  the  body  it  was  pos- 
sible to  deduce  the  truth  of  such  a  doctrine.  In  diseased 
organs  phenomena  are  of  common  occurrence  which  might 
signify,  or  in  some  cases  do  actually  represent,  in- 
creased functional  activity.  In  the  case  of  inflammation, 
swelling  and  redness  are,  in  part,  at  least,  the  expression 
of  enhanced  vital  activity;  fever  is  to  some  extent  due  to 
increased  processes  of  combustion ;  in  valvular  disease  of 
the  heart  which  has  led  to  difficulties  in  the  circulation 
of  the  blood,  the  heart  itself  often  undergoes  a  considerable 
increase  in  size.  It  is  obvious  that  in  these  cases  there 
has  occurred  an  increase  in  the  activity  of  certain  vital 
processes,  but  it  would  be  altogether  erroneous  to  make 
the  changes  in  question  responsible  for  the  occurrence  of 
the  diseases.  In  inflammation  we  have  to  do  with  reac- 
tion on  the  part  of  the  body  against  the  invading  noxious 
influences,  and  above  all  against  micro-organisms,  whicli 
are  by  far  the  commonest  among  the  exciting  causes  of 
inflammation.  On  the  one  hand,  the  noxious  influences 
induce,  in  the  most  sensitive  organic  elements  which  are 
the  factors  of  functional  activity,  certain  changes  whereby 


16  Heredity,  Disease  and  Human  Evolution 

such  activity  is  depressed ;  on  the  other  hand,  in  the  more 
resistant  organic  elements,  they  induce  the  inflammatory 
processes,  which  represent  a  struggle  against  the  excitants 
of  disease,  and  which  must  therefore  be  regarded  as  essen- 
tially favourable  to  the  reacting  organism.  It  is  true  that 
the  inflammatory  reaction  may,  under  certain  conditions, 
have  injurious  results,  but  this  is  not  its  primary  charac- 
ter, being  only  a  secondary  result  of  the  process  in  excess. 
Even  then,  its  injurious  effects  do  not  depend  upon  the 
enhancement  of  vital  activity;  they  depend  upon  the  fact 
that  other  parts  are  interfered  with,  so  that  the  functions 
of  these  are  depressed.  For  example,  inflammation  of 
the  lung  is  not  injurious  per  se,  but  because,  among  other 
reasons,  it  depresses  the  function  of  breathing. 

Again,  the  increase  in  the  processes  of  combustion  char- 
acteristic of  fever  is  not  in  itself  an  exciting  cause  of 
disease;  it  becomes  so  only  in  an  indirect  manner,  when 
the  increased  temperature  impairs  the  functions  of  certain 
organs,  especially  the  brain  and  the  heart. 

Once  more,  when  the  heart  undergoes  enlargement  in 
consequence  of  valvular  disease,  this  change  is  not  per  se 
disadvantageous.  Indeed,  the  enlargement  is  favourable  to 
the  prolongation  of  life,  because  it  effects  a  compensation 
of  the  disturbances  in  the  circulation  that  have  resulted 
from  the  valvular  defect. 

Another  instance  occasionally  invoked  is  that  of  Graves* 
disease.  It  is  apt  to  be  assumed  that  in  this  disease 
the  functional  activity  of  the  thyroid  body  is  notably  in- 
creased, and  that  consequently  an  abnormal  amount  of  the 
substances  formed  in  this  organ  is  poured  into  the  blood 
and  distributed  throughout  the  body,  giving  rise  to  injury 
and  thus  inducing  the  disease.  In  the  first  place  we 
may  object  that  the  explanation  lacks  confirmation,  that  we 
may  well  have  to  do  with  an  altered  rather  than  with  an 
increased  activity  on  the  part  of  the  thyroid  body,  and  that 
this  explanation  is  indeed  far  more  probable.  Apart  from 
this  criticism,  even  if  it  were  established  that  through 


Preliminary  Considerations  17 

the  operation  of  certain  external  influences  the  thyroid 
body  were  stimulated  to  enhanced  activity,  this  would 
not  by  itself  involve  the  existence  of  disease.  For  the 
disease  would  arise  solely  when  the  increased  product  of 
the  thyroid  body  came  to  exercise  an  injurious  influence 
upon  other  organs,  and  above  all  when  it  came  to  depress 
the  functions  of  the  nervous  system.  Similar  considerations 
apply  to  other  cases  in  which  processes  of  increased  vital 
activity  are  supposed  to  be  related  to  the  occurrence  of 
disease.  Such  processes  induce  disease  only  when  they 
depress  the  working  of  some  other  organ  or  organs. 

Finally  it  is  necessary  to  refer  to  one  more  group  of 
processes.  In  patients  suffering  from  mental  disorder  it 
not  infrequently  happens  that  psychical  activity  becomes 
extremely  vigorous,  that  there  is  evidence  of  enormous 
mental  excitement.  It  seems  at  first  sight  as  if  the  disease 
took  the  form  of  a  great  increase  in  the  functional  activity 
of  the  brain.  More  careful  examination  soon  shows,  how- 
ever, that  this  view  is  erroneous.  The  mental  excitement  in 
reality  signifies  the  diminution,  and  even  the  complete 
cessation,  of  orderly  intellectual  activity.  Despite  his 
exaltation,  despite  the  free  flow  of  his  thoughts,  the  person 
suffering  from  mental  disorder  is  incapable  of  making  an 
orderly  use  of  his  mental  experiences.  His  mental  work 
is  far  below  the  normal,  and  indeed  it  ultimately  becomes 
impossible  for  him  to  do  any  mental  work  at  all.  We  see, 
then,  that  in  all  the  cases  in  which  it  was  thought  that  the 
occurrence  of  disease  might  be  referred  to  an  increased  ac- 
tivity of  the  vital  processes,  what  has  really  given  rise  to 
the  morbid  manifestations  is  a  functional  injury. 

Look  at  the  causation  of  diseases  as  we  may,  we  always 
find  that  they  depend  exclusively  upon  a  diminution  or  a 
suppression  -of  the  function,  now  of  one  organ,  now  of 
another,  and  now  of  several  at  once. 

It  results  that  disease  is  the  sum-total  of  depressions  in 
the  vital  functions.  In  their  turn,  these  depressions  depend 
upon  changes  in  the  structure  of  the  tissues. 


18  Heredity,  Disease  and  Human  Evolution 

From  this  definition  of  disease  and  from  its  establish- 
ment by  scientific  considerations  and  experiences  we  may 
deduce  the  fact,  of  which  indeed  the  layman  is  aware  inde- 
pendently of  argument,  that  sick  men  invariably  do  less 
than  healthy  ones,  and  that  therefore  the  former  are  always 
less  valuable  than  the  latter. 

These  conclusions  furnish  the  basis  for  our  subsequent 
observations,  and  we  are  already  in  a  position  to  answer 
the  question  as  to  what  is  the  significance  of  disease  in  rela- 
tion to  the  process  of  human  evolution,  by  saying  that  its 
significance  must  necessarily  be  unfavourabl'e.  For  if  the 
individual  human  being  has  his  value  diminished  by  dis- 
ease, the  community  must  also  suffer.  The  injury  to  the 
community  is  greater  in  proportion  to  the  intensity  with 
which  diseases  prevail  and  in  proportion  to  the  number 
cf  individuals  affected  by  them.  Our  next  task  must  be  to 
gain  a  general  idea  as  to  the  extension  of  diseases.  They 
are  so  extraordinarily  common  that  only  a  minority  of 
the  human  race  can  be  regarded  as  perfectly  healthy,  and 
the  question  may  be  mooted  whether  perfectly  normal 
human  beings  exist.  We  shall  discuss  this  question  first 
of  all.  We  shall  then  consider  the  distribution  of  diseases, 
next  their  manifold  consequences,  and  thereafter  the  means 
that  may  be  employed  to  abolish  them  or  at  least  to  dimin- 
ish their  prevalence.  In  conclusion,  we  shall  inquire  how, 
in  view  of  the  existence  of  diseases,  we  may  best  regulate 
our  lives. 


CHAPTER  II 

THE  FREQUENCY  OF  DISEASES  AND  THE  LIMITS  OP  HEALTH 

If  we  were  to  estimate  the  frequency  of  disease  from 
our  daily  experience  in  intercourse  with  those  engaged 
in  our  own  or  in  other  occupations,  we  might  be  led  to 
believe  that  most  people  enjoy  good  health.  A  large  major- 
ity of  persons  in  active  life  believe  themselves  to  be  healthy, 
and  indeed  are  so,  if  by  health  we  are  to  understand  a 
condition  in  which  people  feel  themselves  free  from  the 
disturbances  we  are  accustomed  to  notice  in  those  who  in 
ordinary  parlance  are  said  to  be  ill,  or  from  the  disturb- 
ances which  are  the  sequels  of  an  illness. 

When,  however,  we  take  into  account  the  fact  that  even 
among  those  who  remain  actively  at  work  many  are  suf- 
fering from  morbid  conditions,  and  that  many  others  are 
by  such  conditions  forced  to  relinquish  their  work,  and 
when  we  look  outside  the  circle  of  those  whom  we  en- 
counter while  going  about  our  ordinary  avocations,  to 
consider  people  in  family  life,  and  those  in  hospitals,  in- 
firmaries, prisons,  etc.,  we  gain  a  very  different  impression. 
This  new  impression  is  greatly  strengthened  if  we  take 
into  account,  not  merely  those  diseases,  passing  by  one 
name  or  another,  which  usually  involve  greater  or  less 
danger  to  life,  but  when  our  notion  of  health  becomes  one 
involving  more  extensive  demands;  if,  that  is  to  say,  we 
regard  as  imperfectly  healthy  all  those  persons  who  in 
one  respect  or  another,  it  may  be  mental  or  it  may  be 
physical,  fall  so  far  behind  the  average  that  they  are  af- 
fected by  injurious  influences  which  others  are  able  easily 
to  withstand.    In  one  aspect  or  another,  their  development 

J9 


20  Heredity,  Disease  and  Human  Evolution 

is  so  defective  that  the  weak  point  gives  way  when  put 
to  a  high  test.  If  we  take  this  as  our  notion  of  health, 
then  we  have  to  add  to  diseases  as  ordinarily  understood 
all  those  lesser  or  greater  divergences  from  the  norm 
which  are  incompatible  with  perfect  health,  all  constitu- 
tional and  congenital  deficiencies,  general  bodily  weakness, 
defective  development  of  the  lungs,  the  heart,  the  sexual 
organs,  imperfect  mental  development,  numerous  psychical 
disturbances  on  the  margin  of  developed  mental  disorder 
which  have  been  so  vividly  described  by  Pelman  in  his 
book  on  Borderland  Mental  States,'^  nervousness,  many  mal- 
formations not  directly  dangerous  to  life,  poorness  of 
blood,  short-sightedness,  colour-blindness,  obesity,  and 
others.  In  the  narrower  sense  of  the  term  disease,  these 
for  the  most  part  are  not  diseases ;  but  if  we  take  a  diminu- 
tion of  functional  capacity  to  be  characteristic  of  the  dis- 
eased state,  we  must  recognise  that  the  disturbances  we 
have  named  all  manifest  this  characteristic.  Human  beings 
thus  affected  are  less  useful  than  others;  they  are  less 
efficient  than  these,  if  not  altogether  inefficient;  and  they 
tend  in  many  ways  to  react  to  the  disadvantage  of  their 
fellows. 

To  all  this  has  to  be  superadded  the  experience  gained 
in  the  post-mortem  room.  In  autopsies  we  note  with  aston- 
ishing frequency  that,  apart  from  the  diseases  which  have 
actually  caused  death,  human  beings  are  not  perfectly 
healthy,  that  they  often  show  divergences  from  normal 
structure,  of  which  they  were  completely  unaware,  which 
ordinarily  do  no  harm,  but  in  certain  circumstances  might 
have  proved  disadvantageous.  We  also  find  on  the  post- 
mortem table  vestiges  of  all  sorts  of  earlier  illnesses  which, 
although  their  presence  was  not  during  life  associated  with 
any  characteristic  symptoms,  yet  cannot  fail  to  have  exer- 
cised an  influence  upon  the  vital  functions  (pleural  adhe- 
sions, which  are  quite  extraordinarily  frequent,  pericardial 
adhesions,  changes  in  the  arteries,   in  the  valves  of  the 

^Pie  psychischen   Grenzzustdnde. 


The  Frequency  of  Diseases  21 

heart,  in  the  heart-muscle,  etc.)-  Most  conspicuous  among 
these  and  most  important  are  tuberculous  processes.  These 
are  sometimes  recent,  and  have  attracted  no  attention  dur- 
ing life ;  while  we  often  find  lesions  of  much  earlier  date, 
which  seem  to  have  altogether  run  their  course  and  which, 
even  if  life  had  persisted,  could  not  have  given  rise  to 
any  further  marked  symptoms  of  disease.  Such  changes 
are  especially  common  in  the  bronchial  lymphatic  glands, 
situated  in  the  thorax  close  to  the  larger  ramifications  of 
the  bronchi.  In  their  oldest  forms  they  appear  as  calcare- 
ous nodules,  whilst  those  of  more  recent  date  are  the 
so-called  caseous  masses,  foci  of  inflammatory  matter  killed 
by  the  tubercle  bacilli.  As  a  rule,  in  this  form,  they  are 
no  longer  dangerous,  but  we  know  that  they  still  con- 
tain living  bacilli.  The  possibility  is  therefore  ever  pres- 
ent that  under  certain  conditions  the  bacilli  may  once 
more  begin  to  multiply,  and  may  lead  to  a  renewed  spread 
of  the  disease.  In  any  case,  their  presence  is  the  proof 
of  the  previous  existence  of  a  circumscribed  tuberculous 
process  which  underwent  arrest  without  causing  extensive 
damage.  It  is  of  especial  interest  to  ascertain  the  fre- 
quency of  these  vestiges  of  past  tuberculosis.  Many  in- 
vestigations have  been  made  on  this  point,  and  their  results 
are  somewhat  discrepant.  One  investigator  reports  that 
he  has  found  such  foci  on  post-mortem  examination  in  the 
bodies  of  95  per  cent,  of  all  adults,  whereas  other  observers 
report  no  more  than  60  per  cent.,  and  express  the  opinion 
that  even  this  high  proportion  finds  its  explanation  in  the 
fact  that  the  bodies  in  question  are  those  of  hospital  pa- 
tients, persons  belonging  to  the  less  well-to-do  classes, 
who  suffer  more  frequently  from  tuberculosis  than  those 
in  easy  circumstances.  Even  if  this  objection  could  be  sus- 
tained, the  general  total  would  not  be  markedly  affected. 
The  classes  that  suffer  especially  from  tuberculosis  are  far 
more  numerous,  and  if  as  many  as  95  per  cent,  among  these 
suffer  or  have  suffered  from  tuberculosis,  the  general  inci- 
dence of  the  disease  is  not  greatly  influenced  by  the  lesser 


22  Heredity,  Disease  and  Human  Evolution 

liability  of  the  well-to-do.  After  all,  we  are  not  much 
concerned  about  a  few  per  cent,  one  way  or  the  other. 
Even  if  no  more  than  90  or  85  per  cent,  of  the  bodies  of 
adults  display  tuberculous  lesions  (and  in  my  personal  ex- 
perience the  lower  figure,  at  least,  is  always  attained),  the 
percentage  remains  an  extraordinarily  high  one.  We  are 
in  a  position  to  assert  that  the  large  majority  of  human 
beings  have  had  their  bodies  invaded  by  tubercle  bacilli, 
and  that  the  result  of  this  invasion  has  been  an  illness  of 
greater  or  less  intensity.  If  we  take  into  account  what  was 
said  above  about  other  morbid  states  of  more  or  less 
frequent  occurrence,  we  are  led  to  the  conclusion  that  it 
will  not  be  easy  to  find  a  human  being  perfectly  healthy 
in  every  respect. 

This  conclusion,  certainly,  can  not  be  applied  to  the  sub- 
jective feelings  of  human  beings.  Many  of  those  affected 
with  trifling  anomalies  feel  perfectly  well  and  are  efficient 
enough.  The  question  of  chief  interest  we  have  to  answer 
is,  how  many  persons  there  are  who  are  really  ill  owing 
to  the  existence  of  one  or  more  of  the  abnormal  conditions 
enumerated  above — how  many,  that  is  to  say,  suffer,  in  con- 
sequence, from  a  real  depression  of  functional  capacity. 
The  estimate  is  naturally  difficult  to  effect,  for  there  exist 
all  possible  transitional  lesser  stages  of  disease  between 
the  severe  forms  and  the  states  regarded  as  representing 
perfect  health.  All  that  we  are  able  to  do  is  to  count  the 
number  of  sick  persons  who  receive  medical  treatment. 
But  however  difficult  it  may  be  to  obtain  trustworthy  data, 
we  possess  one  extremely  useful  source  of  information,  that 
furnished  by  the  records  of  fitness  or  unfitness  for  military 
service.  In  Germany,  about  one  half  of  the  men  legally 
liable  for  military  service  are  rejected  as  unfit.  It  follows 
that  of  a  hundred  men,  fifty  are  either  ill  or  not  perfectly 
healthy.  There  can  be  no  doubt  that  an  examination  of 
women  would  give  similar  results.  From  this  outlook  we 
see  that  only  one  half  of  all  human  beings  twenty  years 
of  age  can  be  regarded  as  healthy.    In  fact,  however,  this 


The  Frequency  of  Diseases  23 

estimate  is  too  favourable,  for  not  all  the  men  accepted  as 
fit  for  service  actually  prove  to  be  so.  From  4  to  5  per 
cent,  of  those  enrolled  are  subsequently  discharged  as  unfit, 
and  of  those  who  remain  after  this  sifting  by  no  means 
all  can  be  considered  in  perfect  health.  Many  deficiencies 
manifest  themselves  only  at  a  later  date,  when  the  time 
comes  to  earn  a  livelihood,  to  enter  into  competition,  to 
take  part  in  the  struggle  for  existence.  It  is  therefore 
beyond  dispute  that  in  the  succeeding  decades  of  life,  in 
which  the  human  being  has  for  the  first  time  to  meet  the 
most  extensive  claims,  in  which  it  becomes  necessary  for 
him  to  demonstrate  his  functional  capacity  on  behalf  of 
himself  and  his  fellows,  the  number  of  invalids  and  of 
those  unable  adequately  to  meet  the  claims  made  upon 
their  energies  greatly  increases.  It  is  only  at  this  period 
of  life  that  many  diseases  dependent  upon  inheritance, 
such  as  gout,  diabetes,  and  mental  disorders,  first  manifest 
themselves;  others,  like  tuberculosis,  now  make  disastrous 
progress.  Now  appear  also  numerous  chronic  and  incur- 
able diseases,  those  which  cause  permanent  and  increasing 
injury,  such  as  inflammations  of  the  kidney,  cirrhosis  of 
the  liver,  various  cardiac  defects,  and  other  disturbances 
of  the  activity  of  the  heart,  diseases  of  the  blood-vessels, 
with  their  manifold  evil  consequences,  cancerous  and  other 
tumours,  syphilis,  the  consequences  of  alcoholism,  of  over- 
exertion, etc. 

The  morbid  conditions  just  enumerated,  when  they  have 
once  manifested  themselves,  render  the  sufferer  useless  or 
impair  his  value  for  the  rest  of  life — gout,  for  instance, 
diabetes,  contracting  kidney,  diseases  of  the  blood-vessels, 
mental  disorder,  etc.  Such  diseases,  whether  present  from 
birth  or  developing  subsequently  in  consequence  of  an 
inherited  tendency,  whether  like  tuberculosis  they  may 
arise  with  or  without  the  existence  of  predisposition,  or 
whether  they  are  induced  in  individuals  previously  healthy 
through  the  operation  of  noxious  influences  in  the  environ- 
ment— such  diseases,  once  they  have  appeared,  are  either 


24  Heredity,  Disease  and  Human  Evolution 

incurable  or  but  partially  curable.  They  give  rise  to  per- 
manent injury. 

We  have  no  trustworthy  data  as  to  the  proportion  of 
persons  thus  diseased  or  diminished  in  value  during  those 
middle  decades  of  life  which  are  the  most  important  to 
humanity.  But  there  can  be  no  doubt  whatever  that  far 
more  than  half,  that  at  least  three-fourths,  of  all  human 
beings  at  this  period  of  life  must  be  said  to  fail  to  attain 
to  the  standard  of  perfect  health. 

We  have  still  to  take  into  account  all  the  transient  newly 
acquired  diseases  which  lay  people  up  for  a  time,  termi- 
nating in  recovery  or  in  death,  or  leaving  behind  them  all 
sorts  of  disastrous  consequences  and  perhaps  permanent 
invalidism.  Even  though  the  majority  of  such  illnesses, 
such  as  inflammations  of  the  lung,  catarrhs,  typhoid,  physi- 
cal injuries,  wound  infections,  etc.,  commonly  leave  no 
permanent  impairment  of  health,  the  interruption  to  the 
working  powers  of  the  patient,  with  its  inevitable  reactions 
upon  those  dependent  upon  him  and  on  wider  circles,  is 
a  very  serious  matter,  and  often  involves  permanent  injury 
to  the  course  of  life.  Such  illnesses  are  extraordinarily 
numerous.  It  is  impossible  to  give  precise  figures,  for  no 
attempt  has  hitherto  been  made  to  ascertain  how  fre- 
quently the  individual  suffers  from  these  transient  affec- 
tions. But  it  is  universally  known  that  we  seldom  meet 
any  one  whose  functional  capacity  has  never  been  im- 
paired by  illness.  The  majority  of  elderly  people  have 
been  ill  very  often. 

All  that  has  been  said  refers  only  to  the  most  important 
period  of  life,  the  middle  decades,  in  which  the  physical 
powers  are  at  their  best.  But  before  this  period  is  at- 
tained death  has  already  reaped  a  rich  harvest.  Every 
one  knows  that  the  mortality  of  children  during  the  first 
year  of  life,  due  above  all  to  intestinal  disorders  dependent 
upon  errors  of  nutrition  and  lack  of  proper  care,  but  due 
also  to  tuberculosis,  syphilis,  etc.,  is  enormous  and  a  scan- 
dal to  our  civilisation.    We  shall  return  to  this  matter  later. 


The  Frequency  of  Diseases  25 

After  the  first  year  of  life,  large  numbers  of  children 
succumb  to  the  common  infectious  diseases,  diphtheria, 
measles,  scarlatina,  whooping-cough,  and  tuberculosis.  This 
involves  a  great  increase  in  the  percentage  of  illness. 

On  the  other  hand,  we  have  to  bear  in  mind  that  after 
middle  age  diseases  become  especially  common,  increasing  in 
frequency  as  years  advance.  This  applies,  first  of  all,  to 
chronic  and  generally  incurable  morbid  states.  So  com- 
mon do  they  become  that  the  enormous  majority  of  old 
persons  display,  not  merely  trifling  disturbances,  but  devel- 
oped morbid  states,  even  if  these  are  not  always  severe. 
As  age  advances,  vascular  changes  become  especially  com- 
mon, the  so-called  calcareous  degeneration  of  the  arteries, 
with  all  the  dangers  it  entails  for  the  brain,  the  heart,  and 
other  organs  and  parts  of  the  body ;  pathological  conditions 
of  the  bones  and  joints,  impairing  the  powers  of  move- 
ment; cancer  in  all  its  forms. 

The  consequences  of  the  diseases  of  old  age,  especially 
those  that  run  a  chronic  course,  are  often  difficult  to  dis- 
tinguish from  such  as  are  the  direct  result  of  old  age  per 
se.  In  both  cases  we  have  to  do  with  a  depression  of  func- 
tional capacity.  Hence  it  has  been  maintained  that  old 
age  must  itself  be  regarded  as  a  disease,  as  a  consequence, 
above  all,  of  defective  circulation  of  the  blood  resulting 
from  alterations  in  the  blood-vessels.  This  view  is  erro- 
neous. At  the  post-mortem  examination  of  the  body  of  the 
oldest  man  or  woman  we  do  not  necessarily  find  any  or- 
ganic changes  of  which  we  can  speak  as  morbid,  apart  from 
the  acute  disease,  inflammation  of  the  lung,  for  instance, 
from  which  the  patient  has  died.  What  we  always  do  find 
in  such  cases  is  a  diminution  in  size  of  all  the  organs  and 
of  the  cells  of  which  they  are  composed,  and,  as  age  ad- 
vances, we  note  with  increasing  frequency  that  the  cells 
are  stained  yellow  and  brown.  But  these  are  phenomena 
attaching  to  the  normal  course  of  life ;  that  is  to  say,  they 
are  physiological  in  character,  but  would  ultimately  extin- 
gui^  life  if  it  were  not  brought  to  an  end  by  some  acute 


26  Heredity,  Disease  and  Human  Evolution 

process.  It  is  true  that  Metschnikoff  contends  that  these 
changes,  which  are  especially  marked  in  the  heart  and  the 
brain,  are  morbid  in  character,  and  that  they  must  be 
referred  to  a  process  of  auto-intoxication  derived  from  the 
large  intestine,  filled  with  faeces  and  micro-organisms. 
This,  however,  is  impossible.  The  large  intestine,  like 
every  other  organ,  so  long  as  it  functions  normally  can 
never  be  a  source  of  injury  to  the  rest  of  the  body.  In 
old  age,  of  course,  it  may  undergo  pathological  changes, 
and  may  then,  like  any  other  diseased  organ,  exercise  an 
injurious  influence  upon  the  body.  This  has  no  bearing 
upon  the  changes  of  old  age.  These  appear  by  rule,  whilst 
in  old  age  the  large  intestine  is  diseased  only  by  exception. 
The  appearance  of  senility  must  rather  be  referred  to  the 
fact  that  the  cells  of  the  various  organs  gradually  lose  their 
vital  capacity  because  their  prolonged  activities  ultimately 
induce  changes  incompatible  with  the  proper  performance 
of  their  functions.  In  the  cells  of  the  brain,  the  heart, 
and  other  organs,  there  occurs  an  accumulation  of  minute 
yellow  granules,  which  must  be  regarded  as  products  of 
tissue  change,  their  presence  impairing  the  activity  of  the 
cells.  It  is  upon  these  granules  that  the  above-mentioned 
brownish  tint  of  the  organs  depends.  This  matter  will  not 
be  further  discussed  here,  since  it  does  not  concern  morbid 
processes  in  the  strict  sense  of  the  term,  but  the  terminal 
results  of  physiological  processes.  Those  interested  in  the 
question  may  refer  to  my  own  earlier  writings,  the  mono- 
graph, Der  Tod  aus  Altersschwdche,^  Bonn,  1908,  and  Alt- 
werden  und  Junghleiben,  ^  Deutsche  Revue,  April,  1912. 
None  the  less,  if  old  age  cannot,  strictly  speaking,  be 
regarded  as  a  morbid  state,  it  is  naturally  not  to  be  de- 
scribed as  one  of  perfect  health.  Invariably,  the  old  man 
or  woman  is  less  functionally  efficient,  often  much  less,  thus 
displaying  the  criterion  that  is  characteristic  of  every  path- 
ological state, 

^  Death  from  Old-Age-Weakvess. 
*  Growing  Old  and  Keeping  Yuuiig. 


The  Frequency  of  Diseases  27 

If  we  take  a  general  view  of  the  considerations  adduced 
in  this  chapter  as  to  the  frequency  of  diseases,  we  are 
led  to  conclude  that,  during  the  middle  decades  of  life, 
during  the  period,  that  is,  mainly  characterised  by  the 
manifestation  of  those  functional  activities  of  chief  impor- 
tance to  the  evolution  of  humanity,  more  than  half  of  all 
persons  lack  sufficient  health  to  enable  them  to  meet  all 
demands ;  that  in  the  case  of  the  remainder,  of  those  ordi- 
narily regarded  as  healthy,  the  majority  are  also  affected 
with  comparatively  trifling  morbid  changes  which  do  not 
impair  functional  activity,  and  whose  existence  is  apt  to 
be  demonstrated  only  on  post-mortem  examination ;  that 
in  advanced  age  the  very  large  majority  of  mankind  suffers 
either  from  a  chronic  disease  or  from  minor  disturbances 
incompatible  with  perfect  health ;  that  hardly  any  one 
escapes  attacks  of  acute  or  curable  illness,  and  that  most 
people  suffer  from  such  attacks  several  or  many  times. 
Finally  we  have  seen  that  in  youth,  on  the  one  hand,  the 
frequency  of  illness  is  especially  great,  and  in  old  age,  on 
the  other  hand,  it  is  so  extremely  high  that  old  men  and 
women  suffer,  with  few  exceptions,  from  definite  morbid 
conditions,  altogether  apart  from  the  fact  that  in  any  case 
their  functional  capacity  is  always  much  less  than  when 
tliey  were  younger.  It  results  that  only  that  minority  of 
human  beings  who  exhibit  during  their  daily  life  no  more 
than  trifling  and  barely  perceptible  morbid  changes,  ap- 
pearing otherwise  healthy,  are  in  a  position  to  devote  the 
whole  of  their  powers  to  the  evolution  of  humanity,  and 
that  the  activity  even  of  these  is  occasionally  interrupted 
by  the  incidence  of  acute  diseases.  All  other  persons  have 
their  functional  activities  permanently  limited  or  com- 
pletely suspended  by  the  pathological  conditions  with 
which  they  are  affected. 

The  considerations  hitherto  adduced  by  no  means  ex- 
haust the  subject  of  the  inadequate  functional  capacity  of 
our  race.  We  have  further  to  ask  whether  those  of  whom 
we  may  speak  as  healthy  in  daily  life  all  really  attain  the 


28  Heredity,  Disease  and  Human  Evolution 

highest  degree  of  functional  capacity  which  might  be  at- 
tained by  human  beings  normal  in  every  respect,  whether 
they  adequately  fulfil  all  the  demands  made  upon  them 
alike  bodily  and  mental.  The  attempt  to  answer  this  ques- 
tion induces  doubts  which  will  be  discussed  in  the  fol- 
lowing chapter. 


CHAPTER  III 

DO  NORMAL  HUMAN  BEINGS  EXIST? 

We  pointed  out  in  the  last  chapter  that  there  are  many- 
persons  who  cannot  be  said  to  be  ill  in  the  strict  sense 
of  the  term,  but  whose  value  is  so  much  below  par  that 
they  readily  give  way  in  one  direction  or  another  when 
extensive  demands  are  made  upon  their  powers,  are  injured 
thereby,  or  become  actually  ill.  It  is  obvious  that  the 
conditions  with  which  such  persons  are  affected  do  not 
constitute  a  sharply  circumscribed  group,  clearly  distin- 
guished alike  from  states  of  actual  disease  and  from  states 
of  perfect  health.  All  possible  transitional  stages  exist 
between  such  conditions  and  disease  on  the  one  hand,  and 
health  on  the  other.  We  meet  with  many  cases  in  which 
persons  stand  on  the  boundary  line  of  disease,  and  when 
the  question  of  classification  arises,  whether  they  are  placed 
upon  one  side  or  the  other  depends  upon  the  observer's 
preference  for  a  stricter  or  more  lenient  view.  Those, 
again,  who  occupy  the  domain  of  the  healthy,  differ  widely 
among  themselves.  They  diverge  more  or  less  extensively 
from  an  ideal  state  of  health,  of  which  admittedly  we 
can  frame  no  more  than  a  theoretical  conception.  This 
ideal  state  is  what  we  speak  of  as  normal,  and  we  have 
now  to  ask  ourselves  if  and  how  it  can  be  defined,  and 
whether  we  may  expect  to  encounter  it  in  the  concrete. 

When  can  we  denote  a  human  being  as  normal?  It  is 
evident  that  in  this  connexion  we  can  think  only  of  healthy 
individuals,  only  of  such  as  are  free  from  constitutional 
or  chronic  disease,  and  who  at  the  time  of  investigation 
are  also  free  from  acute  affections  and  their  consequences. 

29 


30  Heredity,  Disease  and  Human  Evolution 

Such  individuals  can  further  be  regarded  as  normal  in 
the  fullest  sense,  only  when  all  their  organs  are  soundly- 
constructed  on  lines  which  generally  accepted  scientific 
experience  leads  us  to  recognise  as  physiological,  when  all 
these  organs  function  as  we  know  they  ought  to  function, 
when  they  work  together  with  perfect  harmony,  when 
not  one  errs  either  by  excess  or  by  defect  in  point  of 
functional  activity  from  the  mean  degree  which  experi- 
ence leads  us  to  recognise  as  proper.  A  human  being 
who  meets  these  demands  can  be  spoken  of  as  normal,  but 
it  is  evident  that  a  sharp  delimitation  of  this  ideally  con- 
ceived state  is  impossible.  The  state  is  one  separated  by 
innumerable  intermediate  gradations  from  states  that  can 
no  longer  be  regarded  as  normal. 

Does  such  a  theoretically  conceivable  normal  state  exist  ? 
As  regards  isolated  functions,  such  as  cardiac  activity,  or 
memory,  the  question  is  comparatively  easy  to  answer.  We 
often  find  ourselves  able  to  speak  of  these  special  aspects 
of  the  individual  as  normal.  It  is  altogether  different, 
however,  when  we  consider  all  the  functions  at  once,  and 
when  we  examine  any  one  in  order  to  ascertain  whether 
all  these  are  alike  normal.  When  we  do  this  we  are  soon 
forced  to  recognise  that  in  this  sense  the  normal  human 
being  does  not  exist.  First  of  all,  a  great  many  persons 
exhibit  a  general  depression  of  their  mental  functions.  It 
is  clear  that  however  exuberant  their  health  may  seem 
to  be,  such  persons  cannot  be  regarded  as  normal.  If  we 
were  to  admit  this,  we  should  also  have  to  admit  those 
persons  to  be  normal  whose  mental  life  is  in  good  order, 
but  who  suffer  from  considerable  general  bodily  weakness. 

In  all  other  persons  we  find  a  defective  development, 
now  of  one  function,  now  of  another.  This  is  especially 
noteworthy  in  the  intellectual  sphere.  Sometimes  one 
capacity  is  defective,  sometimes  another,  sometimes  several 
are  defective  at  once.  Many  persons  are  competent  for 
some  particular  occupation,  while  incompetent  for  the  per- 
formance of  all  the  other  duties  of  life ;  their  development 


Do  Normal  Human  Beings  Exist?       31 

is  markedly  one-sided.  Such  a  condition  is  incompatible 
with  our  definition  of  normality.  On  the  way  to  such 
extreme  instances  we  find  numerous  transitional  stages. 
Many  persons  are  functionally  competent  outside  their 
own  narrow  sphere,  and  exhibit  an  intelligent  understand- 
ing of  other  questions.  The  more  they  display  such  gen- 
eral aptitudes,  the  more  nearly  do  they  approximate  to 
the  ideal  state ;  but  they  never  attain  it,  for  one  side  will 
always  be  found  comparatively  overdeveloped. 

The  majority  diverge  considerably  from  the  normal. 
Left  entirely  to  themselves,  and  lacking  the  complementary 
assistance  of  their  fellow  men,  likewise  one-sided,  but  in 
other  directions,  they  would  be  unable  to  carry  on  their 
lives  satisfactorily — they  are  not  of  standard  value. 

It  may  be  objected  that  it  is  obvious  that  persons  in 
whom  certain  functions  are  under-developed  are  not  per- 
fectly normal.  There  exist,  however,  in  addition  numerous 
individuals  whose  divergence  from  the  norm  depends  upon 
the  fact  that  this  or  that  capacity  is  developed  to  an  excep- 
tional degree!  In  these  the  harmony  of  development  is 
disturbed,  and  yet  we  cannot  refuse  to  them  the  quality 
of  normality.  A  functional  capacity  developed  to  excess 
must  be  spoken  of  as  super-normal,  and  not  as  sub-normal. 

We  shall,  however,  approach  this  problem  differently  ac- 
cording as  our  attention  is  especially  directed  to  the  well- 
developed  function  itself  or  to  the  condition  of  the  rest 
of  the  organism.  It  is  evident  that  an  increase  in  some 
particular  capacity  cannot  per  se  detract  from  normality. 
One  with  exceptionally  powerful  muscular  development, 
one  with  exceptional  musical  faculty  or  some  other  gift, 
is  not  therefore  necessarily  abnormal.  But  how  often 
do  we  observe  that  an  individual  thus  distinguished  re- 
mains below  average  in  his  other  functional  capacities,  that 
these  fail  to  reach  the  normal  level,  so  that  a  complete 
harmony  of  all  the  faculties  is  lacking.  When  one  function 
is  endowed  to  excess,  the  others  suffer  from  defect.  Thus 
certain  exceptionally  muscular  men,  such  as  athletes  with 


32  Heredity,  Disease  and  Human  Evolution 

a  one-sided  development,  can  by  no  means  be  regarded 
as  normal.  They  are  apt  to  be  clumsy  in  their  movements, 
unfitted  for  the  more  delicate  physical  manipulations,  and 
in  them,  as  a  result  of  long  continued  over  exertion,  the 
heart  gives  out  sooner  than  that  of  an  ordinary  man.  Again, 
those  intellectually  distinguished  in  some  particular  capac- 
ity are  often  less  well-developed,  and  perhaps  altogether 
inefficient,  in  other  respects;  not  infrequently  they  fail  in 
face  of  the  practical  demands  of  life,  and  sometimes  their 
physical  development  is  backward  although  they  cannot 
be  said  to  be  diseased. 

Thus  there  exists  an  enormous  number  of  human  beings 
whom  we  are  forced  to  regard  as  not  completely  normal, 
as  inharmoniously  developed,  although  many  of  these  may 
be  of  the  greatest  use  to  humanity  precisely  on  account  of 
their  one-sided  aptitudes. 

Nor  have  we  to  consider  merely  the  case  of  isolated  indi- 
viduals whose  capacities  are  not  perfectly  normal.  There 
exist  also  whole  groups  in  whom  normality  is  lacking. 
First  of  all  must  be  mentioned  the  lower  races,  which 
remain  at  a  level  long  surpassed  by  the  higher  races,  and 
lag  far  behind  these  in  functional  capacity.  Their  whole 
mental  constitution  is  of  inferior  value,  and  in  various 
respects  they  manifest  a  one-sided  mental  development. 
They  will  not  be  spoken  of  as  diseased,  they  must  be 
termed  healthy,  but  we  cannot  describe  them  as  normal 
in  the  sense  here  given  to  the  term. 

Further,  within  the  limits  of  a  single  race,  even  the 
highest,  there  are  whole  groups  of  human  beings  who 
cannot  be  regarded  as  perfectly  normal.  The  members 
of  these  groups  exhibit  an  incapacity  for  the  development 
of  one  faculty  or  of  another;  or  satisfactory  development 
is  limited  to  some  particular  direction.  Entire  classes 
exist  whose  mental  life  is  altogether  inferior  in  quality  to 
that  of  other  classes,  persons,  for  example,  whose  capacity 
attains  the  normal  in  physical  respects  only,  while  their 
mental  powers  remain  inadequate.    For  example,  the  men- 


Do  Normal  Human  Beings  Exist?       33 

tal  life  of  most  country  folk  is  as  a  rule  altogether  defec- 
tive. If  they  possess  adequate  inborn  aptitudes  in  this 
respect,  their  faculties  are  atrophied  from  lack  of  proper 
exercise.  Similar  conditions  prevail  in  the  case  of  a  large 
proportion  of  manual  workers.  The  monotony  of  their 
daily  occupation,  which  makes  demands  merely  upon  their 
physical  capacities,  leads  to  an  atrophy  of  all  their  other 
aptitudes,  or  at  any  rate  keeps  these  at  a  very  low  level. 
It  is  impossible  to  describe  as  a  normal  human  being  one 
who,  earning  his  daily  bread  by  arduous  manual  labour, 
has  never  found  time  to  develop  his  other  capacities,  who 
for  this  reason  feels  no  need,  when  he  has  slept  and 
refreshed  his  body,  for  any  other  occupation  and  for  the 
perfecting  of  his  own  development.  Now  such  conse- 
quences of  the  one-sided  cultivation  of  faculty  are  common 
to  a  greater  or  less  extent  to  all  occupations.  To  compara- 
tively few  only,  to  those  of  manifold  endowments  and 
independent  position,  is  it  granted  to  look  over  the  high 
walls  by  which  their  working  domain  is  surrounded  and 
to  win  for  themselves  something  of  all  that  exists  without. 
This  is  true,  above  all,  of  mental  development.  Our  edu- 
cation is  altogether  one-sided,  not  only  as  far  as  concerns 
preparation  for  a  definite  profession,  but  often  even 
earlier,  in  our  schools.  This  one-sidedness  inevitably  be- 
comes still  more  marked  when  the  goal  has  been  attained 
and  when  the  man  is  yoked  to  his  professional  task  for 
the  rest  of  his  life.  Hence  arises  the  lack  of  interest  in 
one  group  for  another  and  for  the  community  at  large ; 
hence  the  lack  of  mutual  understanding,  for  those  of  one 
profession  know  nothing  or  very  little  of  those  of  another; 
hence  also  distorted  and  regrettable  judgments  and  the 
supervaluation  of  one  profession  over  another.  It  is 
hardly  necessary  to  give  examples,  but  the  reader  may 
think  how  one-sided  are  the  gi'eat  majority  of  philologists, 
lawyers,  army  officers,  men  of  learning,  officials,  etc.  Such 
orie-sided  development  is  incompatible  with  the  normal 
state.    AVe  have  also  to  remember  that  innumerable  human 


34  Heredity,  Disease  and  Human  Evolution 

beings  are  shut  out  from  marriage  and  are  thereby  excluded 
from  one  of  the  most  important  sides  of  life  with  its  mani- 
fold relationships  and  duties.  Look  again  at  the  various 
orthodox  creeds.  These  impose  on  all  their  adherents  cer- 
tain strict  dogmatic  views,  which  keep  them  remote  from 
numerous  problems  and  activities  of  human  life,  and  which 
are  even  in  open  hostility  with  many  aspects  of  life ;  those 
who  accept  these  limitations  must  become  extremely  one- 
sided, regarding  the  world  from  a  narrow  outlook,  admit- 
ting that  science  has  a  right  to  exist  only  in  so  far  as  it 
harmonises  with  the  preconceptions  of  dogma,  this  involv- 
ing mental  bias  and  prejudice.  It  may  be  objected  that 
no  one  can  approach  the  study  of  science  itself  altogether 
without  preconceptions.  In  a  general  sense  this  is  true; 
but  the  genuine  scientific  investigator  has  no  dogmatic 
shackles,  and  is  ready  at  any  time  to  abandon  his  precon- 
ceptions in  favour  of  more  enlightened  views.  In  this 
sense  he  may  be  said  to  be  free  from  his  own  preconcep- 
tions, to  which,  on  the  other  hand,  the  dogmatist  is  uncon- 
ditionally bound. 

Thus  the  various  classes  of  mankind  lack  harmonious 
development ;  they  are  more  or  less  one-sided ;  they  are 
abnormal. 

Nor  must  we  forget  that  entire  races  may  exhibit  an 
injurious  one-sidedness.  Think  of  jingoism,  of  racial  fa- 
naticism, of  the  one-sided  education  of  children  which  de- 
votes them  to  mental  work  while  neglecting  physical 
culture,  and  the  converse  error,  the  over-valuation  of  sport, 
whereby  national  progress  is  hindered. 

Thus  wherever  we  look  we  observe  a  disadvantageous 
one-sidedness  of  capacities  and  of  cultivation,  a  lack  of 
harmonious  development.  The  majority  of  human  beings 
cannot  be  regarded  as  normal;  a  few  only  can  claim  to 
come  within  the  limits  of  this  conception,  and  none  can  be 
said  to  correspond  to  it  perfectly.  One  person  fails  to 
be  normal  because  he  falls  below  the  average  to  an  injuri- 
ous degree  in  some  or  in  all  capacities;  another,  because 


Do  Normal  Human  Beings  Exist?       35 

his  mode  of  life  and  the  necessities  of  the  struggle  for 
existence  involve  the  atrophy  of  one,  several,  or  all  his 
faculties;  a  third,  because  the  development  of  some  one 
capacity  in  very  great  excess  has  left  all  the  other  capaci- 
ties defective. 

Is  another  and  a  better  state  than  this  attainable  by  the 
human  race?  May  it  not  be  asked  whether  it  is  conceiv- 
able that  all  individuals  might  be  born  with  faculties  sus- 
ceptible of  full  development,  or  that  the  high  or  maximum 
cultivation  of  one  faculty  need  not  necessarily  be  accom- 
panied by  defective  cultivation  of  the  others?  Are  we 
not  forced  to  answer  these  questions  with  a  direct  nega- 
tive, and  to  maintain,  in  especial,  that  the  evolution  of  the 
human  race  is  impossible  in  the  absence  of  one-sidedness 
on  the  part  of  individual  members  of  that  race?  For  the 
conditions  of  life  do  not  permit  of  a  harmonious  and 
equable  development.  Yet  this,  we  are  told,  is  of  no 
consequence  because  human  beings  have  to  display  effective 
functional  capacity,  not  along  many  lines,  but  by  means 
of  the  highest  possible  development  of  isolated  faculties. 
All  this  is  not  untrue,  and  yet  it  is  true  only  to  a  certain 
degree.  It  is  unquestionable  that  an  all-sided  functional 
capacity  is  excluded  from  possibility,  that  one-sidedness 
will  always  persist,  and  that  in  the  near  future  it  will 
certainly  increase.  But  it  is  erroneous  to  suppose  that  this 
one-sidedness  will  necessarily  for  ever  be  so  extreme  as  it 
is  to-day,  so  extreme  that  the  other  aptitudes  atrophy  in 
consequence,  and  that  the  individual  becomes  one-sided 
in  an  exclusive  sense.  To  this  question  I  shall  return.  At 
the  moment  my  concern  is  merely  to  establish  the  fact 
that  excessive  one-sidedness  exists,  and  to  indicate  that  all 
persons  thus  affected,  the  large  majority,  that  is  to  say, 
must  be  described  as  abnormal  precisely  because  they 
exhibit  this  excessive  one-sidedness.  We  have,  however, 
to  recognise  that  a  certain  degree  of  one-sidedness  is  essen- 
tial to  the  evolution  of  the  human  race.  Those  individuals 
only  who  are  fully  cultivated  in  some  particular  direction 


36  Heredity,  Disease  and  Human  Evolution 

can  attain  therein  to  the  highest  functional  capacity  such 
as  is  necessary  for  the  advance  of  the  human  race  as  a 
whole.  Hence  the  individual  must  always  be  one-sided, 
for  the  hig:hest  possible  perfection  of  one  faculty  cannot 
fail  to  involve  defects  in  the  others.  Even  the  man  of 
genius,  who  receives  our  ungrudging  admiration  and  who 
assists  to  so  notable  a  degree  in  the  advance  of  our  race, 
is  poorly  developed  in  other  directions  than  those  charac- 
teristic of  his  particular  endowments.  In  a  great  many 
cases,  indeed,  this  is  not  obvious,  or  we  overlook  it  because 
we  are  interested  only  in  observing  the  healthy  side,  but 
there  are  geniuses  not  a  few  in  whom  the  deficiency  of 
their  other  qualities,  a  deficiency  which  may  be  accentuated 
even  to  the  point  of  disease,  is  plainly  disadvantageous. 
Genius  and  madness  have  been  spoken  of  as  akin,  and  the 
question  of  this  relationship  will  receive  consideration 
later.  For  the  moment  it  suffices  to  point  out  that  the 
individual  in  whom  the  one-sided  development  of  a  par- 
ticular faculty  is  associated  with  inadequate  cultivation 
along  other  lines,  will  often  suffer  if,  because  of  these 
deficiencies,  he  is  unable  to  play  his  part  fully  in  the  gen- 
eral life.  Under  certain  conditions  the  qualities  that  are 
useful  to  humanity  may  become  a  curse  to  their  individual 
possessor.  It  is  only  when  the  other  faculties  are  also 
cultivated  to  the  fullest  possible  degree  that  the  one-sided 
cultivation  of  the  pre-eminent  faculty  will  not  be  injurious 
to  the  individual. 

At  the  present  day,  however,  an  altogether  abnormal 
one-sidedness  commonly  prevails.  The  great  majority  of 
human  beings  are  imprisoned  in  a  narrow  circle  of  activi- 
ties, and  are  thereby  excluded  from  the  many-sidedness  of 
life.  With  comparatively  few  exceptions  individuals  re- 
ceive a  one-sided  education  from  birth  onwards ;  one-sided 
they  live  and  work,  and  one-sided  they  remain  till  death. 
For  them  the  fulness  of  life  in  its  endless  manifoldness 
has  no  existence.  The  peasant,  the  labourer,  the  factory 
hand,  the  small  trader,  and  many  of  those  commonly  sup- 


Do  Normal  Human  Beings  Exist?       37 

posed  to  belong  to  the  cultured  classes,  in  so  far  as  they 
make  no  attempt  to  enlarge  their  capacities,  know  noth- 
ing of  life  beyond  a  small  and  narrow  circle,  and  none 
of  them,  in  view  of  the  widespread  atrophy  which  may 
go  so  far  as  complete  suppression  of  other  branches  of 
activity,  can  be  regarded  as  normal  human  beings. 

Wherein  lies  the  explanation  of  these  lamentable  condi- 
tions? In  part,  unquestionably,  in  the  environing  circum- 
stances in  which  most  of  us  live.  The  struggle  for  daily 
bread,  the  dependent  position  into  which  most  people  were 
born,  enforces  upon  them  a  one-sided  cultivation,  for  thus 
only  are  they  able  to  secure  the  means  of  life.  Their 
lives  run  on  in  an  almost  unbroken  grey  monotony,  and 
thej^  are  excluded  from  participation  in  what  brings  hap- 
piness and  enjoyment  to  others.  Human  society,  which  is 
satisfied  if  the  individual  is  able  merely  to  live,  provides 
no  institutions  to  lift  its  members  above  the  level  of  this 
everyday  uniformity. 

The  needs  for  the  struggle  for  daily  bread  are  not,  how- 
ever, the  only  cause  of  the  trouble.  As  we  have  already 
pointed  out,  and  as  we  wish  to  emphasise  once  more,  edu- 
cation plays  an  important  part.  It  is  almost  always 
undertaken  by  persons,  parents  and  teachers,  who  have 
themselves  suffered  from  a  one-sided  cultivation.  School 
should  provide,  by  means  of  a  many-sided  instruction,  a 
certain  degree  of  general  culture.  In  one  way  or  another, 
however,  the  school  provides  for  some  definite  direction 
of  cultivation.  In  so  far  as  its  influence  is  many-sided, 
this  influence  is  exerted  for  too  short  a  time,  and  is  not 
nearly  as  extensive  as  it  ought  to  be.  Quite  early  in  life 
the  one-sided  cultivation  begins,  as  a  preparation  for  some 
particular  calling.  Such  special  cultivation  is  doubtless 
essential ;  but  too  little  attention  is  given,  and  from  lack 
of  time  inevitably  so,  to  an  enlargement  of  the  faculties 
by  instruction  in  other  directions.  After  leaving  school, 
the  individual  soon  forgets  all  that  has  no  bearing  on 


38  Heredity,  Disease  and  Human  Evolution 

his  specialty  and  thenceforward,  in  the  case  of  a  large 
majority,  the  outlook  becomes  ever  narrower. 

We  have  now  to  ask,  if  we  could  suppose  the  needs  of 
the  struggle  for  existence  not  to  involve  this  one-sided 
development,  whether  all  persons  would  themselves  exhibit 
the  desire  and  the  possibility  to  be  other  than  one-sided. 
We  are  unfortunately  compelled  to  answer  this  question 
in  the  negative.  The  majority  of  human  beings  have 
to-day  neither  impulse  nor  capacity  for  all-sided  develop- 
ment. They  are  subject  to  the  limitations  of  their  inher- 
ited organisation,  whereby  the  individual  activities  are 
predetermined  to  be  one-sided.  Cong.^.iital  predisposition 
is  the  foundation  of  the  individual's  v, ;:ole  development. 
It  is  possible,  and  this  is  a  point  to  which  we  shall  return, 
to  cultivate  an  inborn  quality  by  exercise  or  to  weaken 
it  by  neglect;  but  it  is  altogether  impossible  to  call  into 
existence  a  quality  whose  elements  are  lacking  or  to  culti- 
vate to  a  useful  extent  one  whose  elements  pre-exist  only 
to  a  minimal  degree.  The  inherited  aptitudes  of  individ- 
uals are  extraordinarily  diverse ;  some  are  good,  some 
moderate,  some  altogether  defective.  Upon  these  differ- 
ences depends  the  direction  in  which  the  individual  be- 
comes active;  upon  these  depends  the  lack  of  capacity  or 
impulse  for  all-sided  or  even  many-sided  development; 
upon  these,  also,  depend  the  indolence  and  the  egotism 
which  lead  to  the  neglect  of  all  other  considerations,  and 
to  the  exclusive  cultivation  of  those  faculties  which  pro- 
mote advance  in  the  chosen  occupation.  Primary  defects 
in  inherited  aptitudes  thus  give  rise  to  a  deplorable  one- 
sidedness  which  persists  throughout  life. 

The  needs  of  life,  then,  education,  and  inherited  pre- 
dispositions, render  readily  comprehensible  the  existence  of 
the  one-sidedness  of  which  we  have  to  complain.  We  recog- 
nise why  it  exists,  and  why  under  existing  conditions  its 
existence  is  inevitable.  But  it  is  our  natural  desire  to 
mitigate  it  as  far  as  may  be,  and  to  have  justice  done  to 
the  other  sides.     In  the  exaggerated  form  in  which  it 


Do  Normal  Human  Beings  Exist?       39 

now  prevails,  this  one-sidedness  is  extremely  injurious.  It 
frequently  turns  life  into  a  waste,  or  at  least  has  as  its 
result  that  most  persons  are  dissatisfied  and  fail  to  make 
the  best  use  of  life.  The  individual's  one-sidedness  is 
injurious  also  to  his  fellow  human  beings.  Consider,  for 
example,  that  the  adherents  of  some  particular  religious 
creed  not  infrequently  despise,  contend  with,  and  perse- 
cute, those  who  differ  from  them  in  opinion;  that  a  one- 
sided lawyer  sometimes  regards  an  accused  person,  not 
as  a  human  being,  but  simply  as  an  object  for  the  applica- 
tion of  the  laws,  and  by  so  doing  arrives  at  false  conclu- 
sions; that  the  one-sided  politician  pursues  politics  from 
interested  motives ;  that  morality-fanatics  empty  the  child 
out  with  the  bath ;  that  one-sided  advocates  of  the  emanci- 
pation of  women  ignore  woman's  most  important  function, 
that  of  motherhood,  thereby  endangering  the  future  of  the 
race,  and  being  led  to  adopt  such  methods  as  those  of  the 
militant  suffragettes,  thus  derogating  from  their  own 
human  worth ;  and  so  on.  Not  even  those  who  are  actually 
diseased  breed  mischief  so  extensively  as  do  such  one-sided 
persons,  especially  in  view  of  the  fact  that  in  the  former 
case  we  can  interfere  to  counteract  the  trouble,  whilst  in 
the  latter  case  will  or  opportunity  to  do  this  is  often  lack- 
ing. 

Even  in  their  own  sphere,  extremely  one-sided  persons 
must  often  be  regarded  as  not  completely  normal.  Such 
persons  are  in  many  respects  of  inferior  value,  and  we 
cannot  draw  any  sharp  distinction  between  them  and  those 
who  are  actually  diseased.  We  need  merely  recall  that 
religious  one-sidedness  often  degenerates  into  mental  dis- 
order, as  in  the  flagellants  and  all  others  who  torture 
themselves  from  motives  of  misconceived  piety.  We  see 
the  same  thing  in  the  case  of  the  dancing  manias,  in  the 
care  of  witches  and  their  persecutors,  in  dervishes,  in 
the  self-mutilators  of  the  Skoptsy  sect,  in  cases  of  suicide 
from  religious  motives,  etc.  For  this  reason  in  our  subse- 
quent argument  we  shall  have  to  consider  diseased  persons 


40  Heredity,  Disease  and  Human  Evolution 

and  those  whose  value  is  below  par  from  the  same  point 
of  view. 

This  problem  as  to  the  existence  of  normal  human  beings 
has  further  to  be  considered  in  relation  to  one  particular 
side  of  mental  life,  namely,  that  which  involves  the  moral 
or  ethical  aspect.  It  is  obvious  from  the  first  that  in 
this  respect  individuals  exhibit  extreme  diversity.  When, 
however,  we  go  on  to  ask  how  many  persons  can  be  re- 
garded as  morally  normal,  we  have  first  to  come  to  an 
understanding  as  to  what  we  mean  by  ethical.  Speaking 
generally,  it  is  true  that  a  common  understanding  may 
be  said  to  exist  upon  this  point.  As  regards  some  par- 
ticular action  or  conception,  no  doubt  need  in  most  cases 
arise  as  to  whether  it  is  to  be  called  moral  or  immoral.  But 
we  need  a  brief  and  precise  definition  of  what  is  to  be 
considered  ethical  from  the  standpoint  of  natural  science. 
We  may  best  start  from  the  notion  of  what  is  immoral. 
Much  that  receives  this  name  really  belongs  to  the  sphere 
of  disease.  This  applies  to  criminal  acts,  and  to  the  acts 
of  many  individuals  whose  mental  capacity  is  below  par, 
and  in  whom  the  power  of  distinguishing  between  what 
is  moral  and  immoral  is  either  absent  or  altogether  in- 
sufficient. Here  we  are  concerned  with  diseased  persons, 
but  there  is  no  sharp  boundary  line  between  this  patho- 
logical sphere  and  the  sphere  of  what  is  normal  in  the 
sense  of  our  definition.  Many  tendencies  that  are  not 
normal  rank  as  immoral,  such  as  excessive  egoism,  oppres- 
sion of  the  weak,  the  promotion  of  incompetence,  the  per- 
secution of  others  on  account  of  their  belief,  marked  un- 
trustworthiness,  and  so  on.  None  of  these  characteristics 
are  present  in  the  normal  human  being.  It  follows  that 
everything  which  is  immoral  is  either  diseased,  or  at  least 
below  par  value,  abnormal.  Conversely  we  must  say  that  a 
normal  man  cannot  be  otherwise  than  moral.  In  such  a 
one  all  the  qualities  exist  in  perfect  mutual  harmony,  and 
in  perfect  harmony  also  with  nature,  of  which  his  fellow- 
men  form  a  part.    In  him  no  one  peculiarity  is  developed. 


Do  Normal  Human  Beings  Exists       41 

either  quantitatively  or  qualitatively,  in  such  a  way  as 
to  be  harmful  to  his  own  other  endowments  or  injurious 
to  those  of  his  fellows.  Thus  all  is  moral  which  a  com- 
pletely normal  human  being  thinks  and  does.  We  must 
also  regard  as  moral  everything  that  is  adapted  to  pro- 
mote the  normal  bodily  and  mental  constitution  of  human 
beings.  Immoral,  on  the  other  hand,  is  everything  which 
proceeds  from  the  thoughts  and  actions  that  are  the 
outcome  of  morbid  and  abnormal  behaviour  on  the  part 
of  human  beings,  and  everything  that  tends  to  be  inju- 
rious to  the  normal  physical  and  mental  constitution. 

The  sole  and  exclusive  measure  of  our  conception  of 
moral  and  immoral  is  the  normal  human  being. 

How  large  is  the  number  of  individuals  whom,  in  the 
light  of  these  considerations,  we  may  describe  as  completely 
moral?  Every  one  who  has  contemplated  himself  and  his 
fellows  must  admit  that  the  number  is  certainly  not  very 
large.  It  is  true  that  we  do  not  get  very  far  by  purely 
objective  observation,  which  is  much  less  helpful  in  this 
regard  than  introspection.  A  great  deal  is  hidden  from 
objective  observation,  and  requires  to  be  examined  sub- 
jectively. We  go  on  to  ask,  then,  how  many  individuals 
are  there  who  would  venture  to  describe  themselves  as  moral 
personalities  in  every  respect  1  This  is  a  question  we  neither 
will  nor  can  answer,  and  we  leave  it  to  the  individual  to 
make  his  own  estimate.  If,  however,  we  are  forced  to 
conclude  that  only  a  few  persons  can  be  regarded  as 
moral  in  the  strictest  sense  of  the  term,  we  have  in  this 
case  also,  when  we  wish  to  estimate  the  signifieance  of 
ethical  endowments  in  the  evolution  of  humanity,  to  take 
into  account  the  existence  of  gradations.  There  are  cer- 
tainly numerous  individuals  who  for  practical  purposes 
and  in  relation  to  the  tasks  of  daily  life  may  be  described 
as  moral. 

Summing  up  all  these  considerations,  in  our  answer  to 
the  question  as  to  the  number  of  perfectly  normal  human 
beings,  when  we  add  to  man's  defective  intellectual  endow- 


42  Heredity,  Disease  and  Human  Evolution 

ment  his  more  or  less  developed  and  disadvantageous  one- 
sidedness,  and  bis  possible  etbieal  deficiencies,  tbe  general 
result  is  not  very  favourable.  These  various  defects  are 
unequally  distributed,  and  not  in  such  a  manner  that  they 
appear  all  together  in  one  individual  while  another  is 
quite  free  from  them.  We  find  rather  that  one  person 
is  defective  in  this  direction,  another  in  that;  that  one 
fails  in  one  point,  another  in  many  points.  Intellectual 
and  moral  qualities  are  by  no  means  necessarily  associated, 
some  persons  being  distinguished  for  the  former  and  others 
for  the  latter.  Very  intelligent  men  may  be  extremely 
immoral,  and  those  who  are  highly  ethical  may  exhibit  a 
very  low  level  of  intelligence.  Thus  the  very  large  major- 
ity are  abnormal  in  one  direction  or  another,  and  if  we 
use  our  terms  strictly  we  need  not  hesitate  to  say  that 
completely  normal  human  beings  do  not  exist.  It  must  be 
admitted  that  the  significance  of  this  statement  in  rela- 
tion to  the  evolution  of  our  race  is  less  great  than  the 
plain  sense  of  the  terms  might  seem  to  imply.  There  are 
many  whose  divergences  from  the  normal  are  so  trifling  as 
to  do  very  little  harm.  Yet  in  the  case  of  the  large  major- 
ity there  exists  incapacity  for  the  performance  of  some 
or  all  of  the  tasks  which  the  community  has  to  undertake. 
If  we  now  reconsider  what  was  said  in  the  previous  chap- 
ter about  the  diffusion  of  diseased  states,  and  in  the  present 
chapter  about  the  lack  of  normality,  we  must  admit  that 
there  is  on  one  side  of  the  account  a  quantity  of  deficient 
values  many  times  greater  than  the  counterbalancing  sum 
of  normal  conduct,  and  that  thereby  the  evolution  of  the 
human  race  has  always  been  hindered  and  will  be  hindered 
in  the  future.  In  part  we  have  to  do  with  purely  physical 
disturbances  which  impair  the  individual's  powers  of  co- 
operation with  his  fellows;  in  part,  and  above  all,  we 
have  to  do  with  mental  anomalies  dependent  upon  anatom- 
ical changes  in  the  central  nervous  system.  All  these  in- 
feriorities in  value  are  not  of  importance  solely  to  the 
affected  individual,  for  their  influence  extends  far  more 


Do  Normal  Human  Beings  Exist?        43 

widely.  His  dependents  and  his  nearer  and  remoter  asso- 
ciates, his  contemporaries,  and  posterity,  are  injuriously 
affected  in  manifold  ways.  These  have  to  be  considered 
in  subsequent  chapters. 


CHAPTER  IV 

THE   SIGNIFICANCE   OF   DISEASES   TO  INDIVIDUAL   MEN   AND  IN 
RELATION  TO  THE  FREEDOM  OF  THE  WILL 

The  sick  man  is  less  functionally  capable  than  the 
healthy.  This  is  shown  by  our  previous  exposition,  and  the 
chief  consequences  of  disease  to  the  individual  have  already 
been  pointed  out.     But  more  remains  to  be  said. 

Diminution  in  functional  capacity  is  naturally  most  ob- 
vious in  serious  illness,  and  especially  in  the  case  of  those 
illnesses  whose  onset  is  sudden,  so  that  the  contrast  be- 
tween the  condition  of  health  and  that  of  disease  is  con- 
spicuous. Those  suffering  from  acute  pneumonia,  diph- 
theria, typhoid,  meningitis,  etc.,  are  completely  unfitted 
for  work.  But  the  degree  to  which  the  working  powers 
are  impaired  by  far  less  serious  affections,  such  as  tooth- 
ache, headache,  boils,  or  physical  injury,  is  known  to  us 
all  from  personal  experience. 

The  disadvantageous  influence  of  an  illness  is  obviously 
proportional  to  its  duration.  Pulmonary  tuberculosis,  dia- 
betes, gout,  and  other  illnesses  which  last  for  decades,  cause 
permanent  impairment  of  the  sufferers'  powers.  Such  per- 
manent impairment  is  above  all  the  outcome  of  congenital 
diseases,  and  especially  of  those  which  affect  the  nervous 
system.  The  manifold  psychical  disturbances  associated 
with  the  last-named  not  infrequently  involve  a  permanent 
depression  in  value  throughout  life,  and  may  even  unfit 
the  patient  completely  for  all  activity. 

When  we  recall  what  has  been  said  in  the  previous  chap- 
ters as  to  the  extraordinary  frequency  of  morbid  states, 
brief  and  transient,  enduring,  or  lifelong,  we  see  that  there 

44 


The  Significance  of  Diseases  45 

must  result  an  enormous  detraction  from  working  capacity. 
Hardly  any  one  can  be  found  in  whom  a  short,  long,  or 
permanent  illness  has  not  led  to  the  loss  of  what  he  might 
have  done  had  he  remained  healthy.  Innumerable  is  the 
number  of  those  who  have  had  existence  rendered  difficult, 
and  not  small  the  number  of  those  who  have  thereby  been 
reduced  to  dire  need.  IMoreover,  apart  from  the  direct  con- 
sequences of  illness,  the  joy  of  life  is  thereby  greatly  dimin- 
ished or  even  annulled. 

Functional  capacity  is  impaired,  not  merely  by  dis- 
eases in  the  narrower  sense,  but  in  addition  by  all  the 
abnormal  states  considered  in  the  previous  chapter.  By 
this  we  do  not  mean  that  work  done  in  the  line  of  some 
one-sided  development  of  faculty  is  worse  done,  for  in 
this  direction  it  is  obvious  that  the  abilities  are  usually 
well  developed.  But  the  person  who  suffers  from  an  ex- 
cessivel}^  one-sided  development  is  lacking  in  all  or  in  many 
other  respects,  and  the  values  of  his  existence  are  thereby 
injuriously^  affected. 

Man's  functional  activities  depend  not  merely  upon  his 
capacities,  but  also  upon  the  energy  of  his  will,  and  this 
matter  therefore  requires  particular  attention. 

We  all  know  from  personal  experience  the  unfavourable 
influence  exercised  upon  the  will  by  morbid  conditions  of 
all  kinds.  Our  energy  is  in  abeyance,  or  sinks  to  a  mini- 
mum. It  is  not  merely  that  we  cannot  be  active,  but  very 
often  that  we  do  not  desire  to  be  so.  We  lose  interest 
in  our  ordinaiy  occupations,  they  become  indifferent  to  us, 
we  cannot  be  bothered  with  our  profession,  our  business, 
our  scientific  studies,  although  by  a  serious  effort  we  should 
often  be  enabled  to  attend  to  our  affairs.  The  will  is  par- 
alysed. The  impulse  that  formerly  kept  us  at  work  is 
no  longer  operative. 

Not  only  may  the  will  be  weakened  by  illness,  it  may  also 
in  this  way  have  its  direction  diverted.  This  happens 
especially  in  the  case  of  mental  illnesses,  but  also  in  certain 
bodily  illnesses  when  these  react  especially  on  the  mind. 


46  Heredity,  Disease  and  Human  Evolution 

The  man  who  has  become  mentally  abnormal  feels  im- 
pelled to  abnormal  activities,  to  commit  a  crime,  to  injure 
or  affront  another  man,  to  undertake  some  occupation  he 
knows  nothing  about,  to  play  the  spendthrift,  to  push  him- 
self to  the  front  on  all  occasions,  etc.  He  is  unable  to 
resist  these  imperious  impulses,  unless  indeed  his  judg- 
ment remains  sufficiently  sound  to  enable  him  to  retain  a 
sufficient  degree  of  opposition  to  the  insurgent  desires. 

We  are  accustomed  to  say  of  those  who  are  dominated 
by  such  abnormal  impulses,  that  the  will  is  no  longer 
free.  This  introduces  a  conception  which  requires  careful 
consideration.  It  is  commonly  held  to  be  a  great  good 
to  have  a  free  will.  One  who  can  follow  his  own  will 
finds  satisfaction,  whereas  to  be  hindered  in  the  opera- 
tion of  the  will  is  disagreeable  and  painful.  Now  when 
we  observe  that  a  morbid  condition  may  not  merely  impair 
our  will,  diminish  its  strength,  but  may  also  induce  new 
motives  coercing  our  will  to  exercise  itself  in  undesired 
directions;  when  we  see,  further,  that  all  this  happens  to 
our  fellow  men,  and  that  when  they  fall  ill  their  free 
voluntary  determination  is  often  lost,  that  therewith  may 
disappear  also  the  consciousness  of  its  loss,  so  that  they 
lead  no  more  than  a  blind  impulsive  life — then  we  come  to 
recognise  one  of  the  most  serious  injuries  inflicted  upon 
us  by  illness. 

We  see,  then,  that  the  notion  of  the  freedom  of  the  will 
is  of  the  greatest  importance  in  our  exposition.  The  capac- 
ity of  mankind  for  evolution  depends  to  a  large  extent 
upon  whether  we  really  possess  the  power  to  undertake 
the  tasks  that  lie  before  us,  or  whether  our  will  to  under- 
take these  be  impaired  by  illness. 

Does  freedom  of  the  will  really  exist?  We  know  that 
this  question  has  been  fiercely  debated  from  the  earliest 
times,  but  the  controversy  is  one  upon  which  we  cannot 
enter  here.  And  yet  it  is  impossible  for  us  to  leave  the 
matter  altogether  unconsidered.  It  is  necessary  to  explain 
briefly   what  we   are  to   understand  when   we  speak  of 


The  Significance  of  Diseases  47 


■■to 


the  freedom  of  the  will.  Then  only  shall  we  obtain  a  clear 
view  of  the  manner  in  which  illnesses  affect  the  will,  and 
of  how,  in  this  respect,  they  concern  the  subject  we  are 
considering. 

When  a  man  wills,  his  will  is  always  and  in  all  circum- 
stances conditioned  by  something  which  has  happened  in 
the  past,  by  something  which  is  happening  simultaneously, 
or  by  something  which  is  conceived  as  going  to  happen  in 
the  future.  An  act  of  will  never  arises  out  of  nothing,  as 
something  altogether  new.  It  is  invariably  a  product  of 
certain  conditions,  one  link  in  a  chain  of  successive  mental 
processes.  The  will  does  not  exist  as  a  phenomenon  appear- 
ing suddenly,  and  in  isolation  from  the  rest  of  the  mind. 
In  the  mental  domain,  just  as  in  the  physical,  there  is  per- 
fect continuity,  or  in  other  words  causality;  there  is  no 
interruption,  no  hiatus.  The  fact  is  obvious,  and  yet  it  is 
not  universally  believed  even  to-day. 

In  the  individual,  the  will  is  determined  by  influences 
from  without.  Some  external  impulse  induces  a  reaction. 
In  so  far  as  these  reactions  are  purely  reflex,  we  are  not 
concerned  with  them  here,  but  in  so  far  as  they  are  some- 
thing more,  they  are  acts  of  will.  The  act  of  will  may 
be  very  closely  dependent  upon  the  external  influence,  so 
that  the  man,  apart  from  the  fact  that  the  action  pro- 
ceeds from  himself  and  is  an  outcome  of  his  own  person- 
ality, hardly  seems  to  add  anything  new.  We  see  this,  for 
example,  when  to  an  attack  he  instantly  responds  with  a 
blow.  The  difference  here  between  the  act  of  will  and  a 
reflex  action  is  inconsiderable.  In  most  cases,  however,  the 
external  influence  is  not  transformed  so  shortly  and  simply 
into  an  act  of  will.  Most  commonly  the  man  contributes 
more  or  less  on  his  own  part.  Ilis  individuality  deter- 
mines what  form  the  reaction  shall  take.  When  the  sun 
begins  to  shine  the  will  is  often  immediately  directed 
towards  a  country  walk;  but  frequently  other  motives 
come  into  operation  which  conflict  with  the  primary  de- 
sire, ultimately  inducing  us  to  stay  at  home  and  to  engage 


48  Heredity,  Disease  and  Human  Evolution 

in  some  more  necessary  oeeupation.  Thus  the  constitution 
of  our  own  ego  decides  against  the  external  influences. 

In  other  eases  the  individuality  decides  in  the  absence 
of  any  external  impulse.  The  will  is  formed  out  of  that 
which  lives  and  works  within  us.  Scientific  experiments, 
for  example,  which  we  turn  over  in  our  mind  lead  us  to 
conclusions  which  serve  as  the  stimuli  to  further  investi- 
gations. The  will  then  comes  into  operation  to  direct  us 
towards  the  new  goal.  Again,  our  thought-associations 
lead  us  to  remember  that  it  is  a  long  time  since  we  have 
seen  a  certain  friend,  and  thereupon  our  will  determines 
us  to  pay  him  a  visit. 

An  act  of  will  never  appears  in  absolute  independence ; 
it  is  always  conditioned.  To  this  extent,  therefore,  there 
is  no  such  thing  as  freedom  of  the  will.  No  act  of  will 
can  occur  except  as  a  part  of  some  continuity.  Do  we 
experience  this  as  a  limitation?  By  no  means.  And 
wherefore  not  ?  Because  all  the  conditions  of  the  will  that 
arise  within  ourselves  are  expressions  of  our  own  individ- 
uality, and  are  therefore  felt  by  us  to  be  welcome.  In 
normal  circumstances  our  will  is  always  in  harmony  with 
our  self;  we  cannot  will  in  any  other  way  but  as  the 
expression  of  that  self.  For  this  reason,  the  fact  that 
the  will  is  enchained  in  the  continuity  of  the  conditions 
that  are  operative  within  us  is  never  experienced  as  a 
sense  of  lack  of  freedom.  We  feel  ourselves  free  when  we 
can  follow  our  own  impulses.  The  will  is  free  because  it 
is  the  outcome  of  our  own  individuality,  in  opposition  to 
which  we  are  unable  to  will  at  all.  Free  will  is  the  capac- 
ity of  the  individual  to  act  in  accordance  with  his  own 
individuality.  This  individuality  is  always  and  in  all  cir- 
cumstances dominant,  our  will  is  dependent  upon  it,  and 
to  that  extent  is  not  free.  It  is  true  that  there  not  infre- 
quently occurs  within  us  a  struggle  between  motives,  which 
may  depend  upon  conflicting  peculiarities  of  our  own  ego, 
or  may  be  the  outcome  of  external  influences.  In  such 
cases,  however,  the  more  powerful  motive  is  ultimately 


The  Significance  of  Diseases  49 

decisive,  and  this  is  equivalent  to  the  subordination  of  the 
weaker  portion  of  our  own  individuality.  Upon  this,  in 
these  cases,  the  will  is  therefore  also  dependent. 

What  has  been  said  is  applicable  mainly  to  healthy  per- 
sons. In  the  diseased,  the  conditions  are  somewhat  more 
complex.  Here  all  kinds  of  pathological  motives  are  in 
operation  by  which  the  will  is  determined.  If,  indeed,  we 
regard  these  pathological  motives  as  constituents  of  the 
sick  man's  individuality,  if  we  affirm  that  the  abnormal 
impulses,  perversities,  etc.,  are  expressions  of  his  own 
nature,  then  the  conditions  are  identical  with  those  which 
prevail  in  the  healthy  person.  Sick  man  and  healthy  alike 
act  in  accordance  with  their  own  individualities.  No  prac- 
tical objection  can  be  made  to  this  point  of  view.  The 
significance  of  diseases  is  then  manifest;  they  determine 
the  thoughts  and  actions  of  human  beings. 

Yet  we  cannot  rest  perfectly  content  with  this  point  of 
view,  if  only  for  the  reason  that  we  should  then  have  to 
regard  diseases  as  essential  human  qualities,  attaching  to 
humanity  for  all  time.  We  must  therefore  look  for  a  more 
satisfactory  conception,  and  we  shall  find  it  in  certain  the- 
oretical considerations  which,  indeed,  cannot  always  be 
easily  translated  into  practice. 

Let  us  start  with  the  healthy,  normal  human  being.  In 
such  a  one  all  desires,  impulses,  voluntary  activities,  are 
in  mutual  harmony  and  in  hannony  with  those  of  his 
healthy  fellow  beings.  Being  parts  of  a  great  healthy 
whole,  no  contradiction  can  arise  among  them.  In  such 
persons,  the  individuality  can  manifest  itself  altogether 
without  hindrance;  in  our  sense  of  the  term,  the  will 
is  free.  All  that  exists  in  them  belongs  to  them ;  we  can- 
not conceive  of  anything  being  taken  away  without  the 
man's  losing  something  from  his  personality.  It  is  alto- 
gether different  when  diseased  or  abnormal  motives  come 
into  play,  or  when  one  of  the  qualities  becomes  influenced 
by  disease.  Then  we  have  the  impression  of  some  foreign 
element  in  action,  which  exercises  a  restrictive  influence, 


50  Heredity,  Disease  and  Human  Evolution 

whereby  the  will  of  the  healthy  individual,  or,  to  speak 
more  strictly,  of  those  portions  of  the  individuality  that 
remain  healthy,  is  hindered  in  its  operation. 

We  can  conceive  the  abnormal  characteristic  removed, 
we  can  take  it  away  in  thought,  without  thereby  inflicting 
any  loss  on  the  man.  This  is  obvious,  above  all,  in  the 
case  of  physical  illness,  which  always  appears  to  us  as 
something  not  properly  belonging  to  the  body,  as  some- 
thing superadded,  as  foreign.  Such,  indeed,  is  its  nature. 
The  normal  healthy  human  being  is  a  type,  and  this  type 
is  deformed  by  the  disease. 

Nor  are  the  conditions  notably  different  where  the  men- 
tal individuality  is  concerned,  although  here  the  contrast 
between  the  healthy  and  the  diseased  is  often  made  mani- 
fest with  much  greater  difficulty,  for  the  reason  that  the 
characteristics  now  run  into  one  another  to  a  far  greater  ex- 
tent, and  because  at  least  the  slighter  divergences  from 
completely  normal  behaviour  masquerade  as  sterling  pe- 
culiarities of  the  individuality.  If,  however,  we  sift  the 
matter  to  the  bottom,  and  if  we  take  into  account,  above 
all,  obviously  abnormal  motives,  we  perceive  in  this  case 
also  the  contrast  between  the  healthy  and  the  diseased. 
The  man  himself,  in  so  far  as  he  still  retains  powers  of 
self-observation,  feels  the  pathological  motives  as  some- 
thing of  a  disturbing  character,  something  hostile  to  him- 
self ;  he  cannot  escape  them ;  only  with  difficulty,  if  at 
all,  only  with  internal  struggle,  can  he  follow  the  deter- 
minations of  his  own  individuality  in  so  far  as  this  still 
remains  normal.  Thus  the  normal  will  is  hindered  in  its 
operation,  and  in  advanced  stages  of  the  illness  is  alto- 
gether suppressed.  Pathological  motives,  such  as  those 
of  the  criminal,  are  then  solely  dominant,  and  the  freedom 
of  the  will  is  in  complete  abeyance.  This  is  the  case  be- 
cause there  no  longer  exists  a  normal  individuality,  of 
which  alone  free  will  is  the  outcome. 

This  is  especially  plain  in  the  case  of  coercive  ideas,  or 
obsessions.     These  control  the  voluntary  life  either  per- 


The  Significance  of  Diseases  51 

manently  or  periodically.  In  many  cases,  the  patient 
knows  himself  to  be  no  longer  free,  and  this  often  makes 
him  unhappy.  Similar  considerations  apply  also  to  other 
marked  mental  disorders.  They  limit  the  individuality, 
and  shackle  the  will  in  some  particular  direction.  Espe- 
cially is  this  true  of  cases  of  intermediate  degrees  of  sever- 
ity, for  in  the  most  serious  types  of  mental  disorder  will 
can  no  longer  be  said  to  exist,  while  in  the  slighter  mani- 
festations of  disease  the  abnormal  motives  may  be  com- 
pensated or  altogether  overcome  by  healthy  ones.  Impulses 
to  crime  may  fail  to  come  into  operation  because  they  are 
conquered  by  simultaneously  recognised  ethical  motives,  or 
owing  to  the  recognition  that  punishment  will  follow,  or 
as  a  result  of  the  impressions  left  by  education.  In  such 
cases,  when  a  man  overcomes  his  bad  impulses  he  feels 
himself  to  be  free  because  he  helps  the  normal  side  of  his 
nature  to  conquer,  because  he  either  follows  his  own  inborn 
better  impulses  or  those  which  education  and  instruction 
have  made  a  part  of  his  normal  self.  He  does  not  feel 
the  influence  of  these  factors  as  coercion,  but  as  something 
corresponding  to  his  own  inner  nature.  Yet  he  is  just  as 
dependent  upon  these  normal  motives,  as  he  is  dependent 
in  other  instances  in  which  the  morbid  impulses  gain 
control. 

When,  finally,  we  turn  to  consider  the  most  trifling  devi- 
ations from  the  normal,  little  peculiarities  and  oddities,  it 
is  not  difficult  to  see  that  in  these  cases  also  there  is  some- 
thing foreign  in  operation,  that  it  is  as  foreign  elements 
that  they  press  to  the  front  and  enter  more  or  less  into 
control  of  the  voluntary  life. 

We  see,  then,  that  all  mental  disturbances,  slight  or 
severe,  lead  to  the  suppression  or  limitation  of  what  we 
have  termed  the  freedom  of  the  will,  that  is  to  say,  of  the 
capacity  of  the  individual  to  act  in  accordance  with  his 
own  individuality,  or,  as  we  may  express  it  in  virtue  of 
the  previous  considerations,  of  the  necessity  (not  felt  as  co- 
ercion) to  follow  the  dictates  of  the  individuality.    Hence 


52  Heredity,  Disease  and  Human  Evolution 

the  diseased  and  abnormal  human  being  lacks  freedom  of 
the  will.  He  is  dominated  by  the  necessity  to  yield  to  the 
morbid  motives,  while  his  obedience  to  healthy  motives  is 
impaired. 

It  is  now  necessary  to  observe  that  anomalies  of  the 
mental  life  are  so  extraordinarily  common  that  hardly  any 
one  exists  who  displays  not  the  slightest  deviation  from 
the  normal.  Hence  there  exists  an  enormous  total  of  un- 
freedom  of  the  will. 

This  total  becomes  even  greater  if  we  no  longer  confine 
our  examination  to  the  mental  life,  for  all  bodily  disorders 
have  a  more  or  less  restrictive  influence  in  respect  of  free 
will.  We  referred  above  to  the  everyday  experience  that 
headache,  toothache,  and  other  trifling  affections,  are  felt 
to  paralyse  our  energies.  How  much  more  powerfully  op- 
erative in  this  direction  are  those  serious  illnesses  that 
turn  the  thoughts  unceasingly  in  particular  directions, 
often  causing  the  sufferer  to  think  of  nothing  but  his  own 
ego,  making  him  weary  of  life,  and  depressing  his  will 
power.  It  is  not  necessary  to  discuss  the  matter  in  detail. 
To  every  one  who  has  watched  invalids  or  has  himself 
been  ill,  it  is  a  familiar  experience. 

We  learn,  then,  that  the  influence  of  diseases  upon  the 
individual  sufferers  is  enormous,  so  great  that  the  gi-avity 
of  their  consequences  cannot  be  overestimated.  The  vast 
majority  of  human  beings  experience  therefrom  a  loss  of 
functional  capacity  of  shorter  or  longer  duration,  and 
sometimes  lasting  through  the  whole  of  life.  No  less  exten- 
sive than  this  direct  loss  is  the  indirect  loss  which  results 
from  the  diminution  of  energy,  from  the  limitation  of  will ; 
for  will  is  an  outflow  from  the  healthy  portion  of  person- 
ality, and  when  will  is  in  abeyance  even  those  who  are 
best  endowed  by  nature  are  unable  to  devote  themselves  to 
active  work  on  behalf  of  the  progress  of  the  human  race. 
To  these  must  be  added  an  even  more  serious  trouble,  the 
appearance  of  morbid,  abnormal,  unethical  motives,  which, 


The  Significance  of  Diseases  53 

again,  on  the  one  hand  restrict  the  operation  of  the  normal 
will,  and  on  the  other  bring  the  individual  into  manifold 
conflict  with  himself  and  his  environment,  and  thus  inflict 
upon  him  more  or  less  serious  injury. 


^ 


CHAPTER  V 

THE  SIGNIFICANCE  OF  DISEASES  TO  SOCIETY 

The  primary  influence  of  every  disease  is  exerted  on 
the  individual  patient,  causing"  sometimes  trifling  and 
sometimes  serious  injury,  and  sometimes  terminating  his 
existence  altogether.  But  the  influence  of  disease  extends 
far  beyond  the  individual,  not  infrequently  to  regions  alto- 
gether outside  our  ken ;  it  may  affect  the  sufferer 's  depend- 
ents, it  may  affect  numerous  other  persons,  it  may  affect 
posterity  for  untold  generations.  This  extended  influence 
is  exerted  in  a  twofold  manner.  In  the  first  place,  the  sick 
man  is  no  longer  functionally  capable  of  fulfilling  the  ex- 
pectations of  his  social  environment ;  and,  in  the  second 
place,  the  disease  itself  may  be  transmitted  to  other  indi- 
viduals. Both  of  these  matters  need  detailed  consideration, 
and  the  present  chapter  will  be  devoted  to  an  examina- 
tion of  the  significance  of  diseases  for  the  sufferer's  healthy 
fellow-men,  of  the  injuries  inflicted  by  the  diseased  indi- 
viduals upon  their  immediate  associates  and  upon  others, 
and  of  the  injuries  that  arise  from  the  actual  transmission 
of  disease  from  the  sick  to  the  healthy. 

The  patient's  immediate  associates  suffer  first  of  all  from 
sympathy  with  his  sufferings  and  from  the  need  to  care 
for  his  life.  Every  one  who  has  known  what  it  is  to  have 
a  near  relative  seriously  ill  is  well  aware  how  the  family 
and  a  wider  circle  of  human  beings  (varying  in  extent  with 
the  sufferer's  position)  is  sympathetically  affected.  Every 
one  has  seen  how  the  pleasures  of  life  and  work  are  dimin- 
ished for  the  invalid's  associates,  and  how  greatly  their 
activities  are  impaired  in  consequence  of  the  attentions 

54 


The  Significance  of  Diseases  to  Society    55 

they  have  to  pay  to  him.  Should  the  illness  result  in  death, 
the  effect  on  the  associates  is  yet  more  lasting,  and  may 
sometimes  endure  for  years. 

Moreover,  in  numerous  instances,  the  means  of  sub- 
sistence of  the  sick  man's  associates  are  lessened  or  even 
altogether  withdrawn,  in  consequence  of  the  expenses  at- 
tendant on  the  illness  and  owing  to  the  loss  of  earning 
capacity. 

The  disadvantages  extend  far  beyond  the  family.  The 
sick  man  is  unable  to  perform  those  services  to  his  fellow- 
men  which  he  would  have  performed  had  his  health  re- 
mained good.  The  loss  in  this  regard  is  more  important 
in  proportion  as  the  person  affected  with  illness  was  more 
highly  developed,  and  in  proportion  therefore  as  he  was 
able  to  do  more  for  the  community  at  large. 

In  addition,  numerous  other  disadvantageous  results 
have  to  be  considered. 

In  very  many  cases,  the  activities  that  are  the  outcome 
of  the  morbid  state  are  directly  injurious  in  manifold  ways 
to  those  in  the  sufferer's  environment.  Persons  affected 
with  mental  disorder,  so  long  as  the  nature  of  their  illness 
is  not  recognised  and  they  are  allowed  to  remain  at  large, 
are  a  continual  trouble  to  their  families,  which  are  often 
brought  to  ruin ;  they  commit  offences  against  morality, 
becoming  homosexual,  for  instance,  and  the  prey  of  black- 
mailers ;  commit  misdeeds  of  all  kinds,  theft,  arson,  etc. ; 
make  unceasing  complaints,  becoming  troublesome  and 
dangerous  from  delusions  of  persecution.  Consider  also 
the  so-called  ''born  criminals,"  who  continually  relapse 
into  crime,  and  the  alcoholics,  who  in  a  state  of  intoxica- 
tion frequently  commit  serious  punishable  offences.  Since 
the  importance  of  alcoholism  is  especially  great,  this  mat- 
ter deserves  fuller  consideration.  The  objection  might  be 
made  that  alcoholic  intoxication,  being  the  expression  of  a 
mere  transient  poisoning,  is  not  comparable  to  mental  dis- 
orders, and  that  it  must  be  placed  in  a  different  category. 
But  in  drunkenness  there  always  exists  a  mental  disorder, 


56  Heredity,  Disease  and  Human  Evolution 

even  though  this  is  of  but  transient  duration.  In  conse- 
quence of  this  disorder,  the  man's  value  is  temporarily 
diminished,  and  the  inhibitions  are  suppressed  that  under 
normal  conditions  prevent  the  manifestation  of  morbid 
mental  peculiarities.  In  a  state  of  alcoholic  intoxication 
the  worse  sides  of  the  individuals  come  to  light,  and  to  this 
extent  the  proverb  in  vino  Veritas  has  its  justification. 
Drunkenness  shows  us  human  beings  with  the  wrappings 
off,  and  in  contemplating  its  manifestations  we  often  feel 
that  these  are  not  evoked  solely  by  the  alcohol.  The  effect 
of  the  drug  is  merely  to  lead  to  the  display  of  all  those 
characteristics  which  remained  hidden  when  the  drunkard 
was  sober.  This  is  proved  by  the  fact  that  the  effects  of 
intoxication  vary  greatly  in  different  individuals.  The 
normal  human  being,  or  at  any  rate  one  free  from  morbid 
predispositions,  is  not  led  by  alcohol  to  the  commission  of 
crime ;  but  it  is  otherwise  in  the  case  of  those  whose  psychi- 
cal life  was  previously  disordered,  and  whose  morbid  pre- 
dispositions are  now  given  free  rein.  The  fact  is  not  con- 
tested that  in  consequence  of  the  long  continued  and  exces- 
sive use  of  alcohol  even  a  healthy  individual  may  gradu- 
ally become  of  inferior  value  and  may  develop  morbid 
tendencies.  On  the  other  hand,  it  must  not  be  forgotten 
that  a  truly  normal  human  being  would  hardly  become 
addicted  to  the  immoderate  use  of  alcohol. 

The  enormous  significance  of  alcoholism  in  relation  to 
the  commission  of  major  and  minor  offences  has  of  late 
years  been  proved  by  temperance  reformers  and  by  the 
inquiries  they  have  initiated.  In  an  essay  by  Popert  it  is 
stated  that  according  to  investigations  made  by  Baer,  in 
the  year  1876,  of  32,837  prisoners  confined  in  120  German 
prisons,  13,706  had  committed  the  punishable  offence  while 
under  the  influence  of  alcohol,  and  that  every  year  in  Ger- 
many no  less  than  180,000  persons  are  charged  with  of- 
fences committed  while  under  the  influence  of  alcohol. 

It  is  only  in  a  certain  proportion  of  those  suffering  from 
mental  disorder  that  the  serious  consequences  to  which 


The  Significance  of  Diseases  to  Society    57 

allusion  has  here  been  made  are  entailed  upon  the  suf- 
ferer's fellows.  In  the  others,  and  in  cases  of  physical 
illness,  no  such  consequences  ensue.  But  in  those  thus 
excepted,  as  well  as  in  many  in  the  first  category,  other 
serious  disadvantages  arise.  All  invalids  are  partly  or 
altogether  unable  to  care  for  their  own  existence,  or  to 
take  the  necessary  steps  for  the  proper  management  of 
their  illness  and  for  the  attainment  of  a  cure.  They  re- 
quire to  be  cared  for,  often  for  a  long  time  and  very  thor- 
oughly, whereby  claims  are  made  upon  the  energies  of  the 
patient's  associates  or  upon  those  of  specially  engaged 
nurses  who,  if  illness  did  not  exist,  could  employ  their 
faculties  more  usefully  in  other  spheres.  In  a  great  many 
cases  such  care  has  to  be  given  for  the  whole  of  life,  which 
may  be  long.  Let  us  endeavour  to  understand  clearly 
what  this  signifies.  The  care  for  individuals  who  from 
birth  onwards  are  useless  alike  mentally  and  physically, 
who  for  themselves  and  for  their  fellow-creatures  are  a 
burden  merely,  persons  of  negative  value,  is  a  function 
altogether  useless  to  humanity,  and  indeed  positively  in- 
jurious. In  these  cases,  the  attendants  lack  even  the  per- 
sonal satisfaction  felt  by  those  who  are  caring  for  the 
sufferers  from  transient  illness,  that  they  are  helping  to 
keep  alive  individuals  of  a  more  or  less  definite  value.  In 
the  instances  now  under  consideration  the  care  seems  pur- 
poseless. I  do  not,  of  course,  mean  to  imply  that  these  in- 
valids should  be  left  uucared  for.  I  am  merely  contem- 
plating the  possibility  that  illnesses  of  this  character  might 
after  all  not  exist,  and  that  with  their  suppression  the 
attendants  would  become  superfluous.  Those  who  are  now 
ill  could  then  themselves  take  part  in  the  work  of  the 
community,  and  their  attendants  could  be  no  less  usefully 
employed,  whereas  at  present,  from  the  general  outlook 
of  humanity,  the  energies  of  these  latter  are  simply  wasted. 
Our  enumeration  of  the  disadvantages  and  injuries  en- 
tailed by  illness  upon  society  is  still  far  from  complete. 
In  the  majority  of  instances  the  deficient  physical  or  men- 


58  Heredity,  Disease  and  Human  Evolution 

tal  functional  capacity  of  the  invalid  entails  pecuniary 
losses  upon  his  immediate  associates.  Often  these  losses 
are  extensive  and  even  irreparable,  and  death  may  rob  the 
family  of  the  bread-winner.  In  part,  indeed,  though  by 
no  means  completely,  this  disadvantage  is  compensated  by 
insurance.  Even  to-day,  in  cases  of  long-lasting  illness, 
and  where  death  ensues,  the  family  is  often  reduced  to 
dire  poverty.  This  arises  not  simply  from  loss  of  earn- 
ings, but  on  account  of  the  extraordinary  expenses  requi- 
site to  provide  medical  attendance,  nursing,  and  medica- 
ments. Certainly  these  evil  consequences  for  the  family 
are  now  far  less  serious  than  in  former  times.  A  system 
of  national  insurance  provides  for  the  expenses  of  illness, 
and  hospitals  see  to  the  nursing.  But  the  money  must 
come  from  somewhere,  being  furnished  in  part  by  the  in- 
sured, in  part  by  the  employer,  in  part  by  the  municipality 
or  the  state,  and  in  part  by  charity.  Even  if  the  immediate 
associates  of  the  invalid  are  less  affected  by  this  burden 
than  was  formerly  the  case,  the  community  still  suffers. 
We  now  take  this  as  a  matter  of  course,  and  we  seldom 
endeavour  to  represent  clearly  to  ourselves  what  enormous 
sums  are  thus  expended  which,  if  all  human  beings  were 
healthy,  might  be  devoted  to  the  general  interest.  A  few 
examples  may  be  given.  An  investigation  made  by  Irving 
Fisher  in  New  York  shows  that  in  the  United  States  of 
America  138,000  persons  die  every  year  of  consumption. 
The  loss  in  earning-power,  and  the  additional  expenses 
which  this  involves,  are  estimated  by  Fisher  at  £200,000,- 
000.  Two  hundred  million  sterling!  What  services  to 
human  development  might  be  provided  by  all  this  money 
if  we  were  freed  from  the  burden  of  consumption.  Con- 
sider, too,  that,  proportionally  to  population,  what  has 
been  said  of  the  United  States  is  applicable  to  all  the 
countries  of  the  world.  For  consumption  occurs  every- 
where in  about  the  same  proportions.  In  Germany,  the 
yearly  deaths  from  consumption  number  about  120,000. 
Moreover,  the  disease  is  exceptionally  prevalent  during  the 


The  Significance  of  Diseases  to  Society    59 

most  vigorous  years  of  life.  Of  the  deaths  that  occur  dur- 
ing these  years,  about  one  fourth  are  due  to  consumption. 

Estimates  also  exist  as  to  the  incidence  of  typhoid,  a 
disease  far  less  disastrous  to  humanity  than  tuberculosis, 
both  in  respect  of  its  comparative  infrequency  and  of  its 
much  briefer  duration.  Kirchner  estimates  that  the  46,170 
typhoid  patients  of  the  year  1900  (in  Germany)  cost,  in 
nursing  and  in  the  burial  of  the  dead,  about  £500,000.  He 
further  estimates  the  annual  cost  of  venereal  diseases  at 
about  £4,500,000. 

Lomer  has  made  an  estimate  for  mental  disorders.  He 
shows  that  in  public  institutions  in  Prussia  during  the 
year  1900  nearly  60,000  lunatics  were  cared  for,  and  that 
this  involved  a  cost  of  £1,500,000.  If  we  add  to  this 
the  expenditure  of  the  other  states  of  the  German  confed- 
eration, we  obtain  a  total  for  Germany  of  £2,500,000.  Lo- 
mer further  estimates  the  cost  of  lunatics  cared  for  in 
private  institutions  at  another  £2,500,000,  so  that  the  total 
annual  cost  of  mental  disorders  in  Germany  amounts  to 
£5,000,000.  The  costs  of  administration  for  the  provision 
of  doctors,  officials,  nurses,  and  attendants  are  not  included 
in  this  calculation.  "This  is  a  colossal  total,  and  we  have 
to  remember  that  all  this  expenditure  is  of  use  only  in  a 
negative  sense,  effecting  merely  the  segregation  of  these  in- 
valids from  the  social  organism.  No  results  of  positive 
value  are  derived  from  the  enormous  drain  upon  the 
public  purse." 

Pelman  gives  a  characteristic  example  from  the  life 
history  of  a  single  family.  Dugdale,  an  American  inves- 
tigator, came  across  six  members  of  this  family  in  prison. 
He  traced  back  the  family  records  to  1740,  and  was  able  to 
ascertain  the  fate  of  709  of  its  members.  As  a  whole  they 
had  spent  116  years  in  prison,  and  had  been  supported 
by  the  public  during  734  years.  In  the  75  years  to  which 
the  investigation  extended  they  had  cost  the  State  £250,000. 

These  examples  will  suffice.  They  make  alarmingly 
plain  the  incredible  magnitude  of  the  expense  entailed  by 


60  Heredity,  Disease  and  Human  Evolution 

illness  upon  the  family  and  upon  the  community  at  large. 
If  we  take  further  into  consideration  that  invalids  are 
often  a  hindrance  to  their  families  in  various  other  ways, 
that  owing  to  their  illness  their  fellow-men  are  deprived 
of  valuable  services,  that  they  inflict  upon  their  fellows 
countless  injuries  of  other  kinds,  that  they  have  to  be 
cared  for  by  innumerable  persons  whose  energies  might  be 
better  employed,  the  total  of  the  disadvantages  entailed  by 
illness  upon  society  becomes  immeasurably  great. 

In  a  veiy  large  number  of  instances,  in  the  case  of  the 
infectious  diseases,  the  incidence  of  the  illness  is  not  con- 
fined to  the  person  first  affected,  for  the  disease  itself  is 
transmitted  to  the  sufferer's  fellows,  owing  to  the  fact 
that  the  exciting  causes,  micro-organisms  for  the  most  part, 
but  sometimes  other  living  creatures,  are  actually  com- 
municated from  person  to  person.  The  methods  of  trans- 
mission are  extraordinarily  diverse.  The  exciting  causes 
of  disease  may  be  transmitted  by  direct  contact  from  the 
sick  body  to  the  healthy  one.  In  the  case  of  the  diseases 
dependent  upon  wound-infection  it  often  happens  that  a 
healthy  individual  sustains  some  slight  injury  while  per- 
forming an  operation,  a  surgical  dressing,  or  a  post-mortem 
examination,  thus  introducing  the  micro-organisms  into  his 
own  body.  A  medical  man,  again,  who  has  some  infective 
process  going  on  in  one  of  his  fingers  may  infect  another 
person  in  the  course  of  an  examination,  while  attending 
a  woman  in  child-birth,  for  instance.  Anthrax  is  mainly 
acquired  through  wounds  received  while  handling  the 
carcasses  and  hides  of  animals  which  have  been  affected 
with  this  disease.  In  the  case  of  many  of  the  infectious 
diseases,  such  as  measles,  scarlatina,  and  smallpox,  we  are 
still  ignorant  of  the  precise  means  by  which  the  infection 
is  transmitted.  It  may  take  place  directly  from  person 
to  person,  but  it  may  also  be  effected  by  the  intermedia- 
tion of  other  individuals,  and  by  that  of  inanimate  objects 
(articles  of  clothing,  toys,  etc.)  which  have  been  in  con- 
tact with  the  patients.     In  the  case  of  diphtheria  and  of 


The  Significance  of  Diseases  to  Society    61 

whooping-cougli  the  same  methods  of  infection  also  pre- 
vail, but  in  the  transmission  of  these  diseases  direct  infec- 
tion as  a  result  of  coughing,  by  which  mucus,  etc.,  con- 
taining the  infective  organisms  is  expelled  by  the  patient 
and  then  in  one  way  or  another  transferred  to  the  healthy, 
plays  a  far  more  important  part.  Similarly  in  the  case 
of  tuberculosis,  the  danger  is  ever  present  of  the  transmis- 
sion of  the  disease  through  expectoration  and  coughing, 
whereby  materials  containing  tubercle  bacilli  are  dissem- 
inated in  the  air  and  may  be  inhaled  by  healthy  indi- 
viduals. There  is  also  a  danger  that  in  ordinary  conver- 
sation minute  drops  of  fluid  may  be  expelled  from  the 
mouth ;  in  the  tuberculous  these  often  contain  bacilli  which 
may  then  be  inhaled  by  healthy  persons.  Diphtheria  and 
whooping-cough  may  likewise  be  transmitted  in  this  fash- 
ion. Tuberculosis  is  disseminated  in  yet  other  ways.  The 
bacilli  expelled  by  the  patient  are  deposited  upon  furni- 
ture, articles  of  clothing,  the  floor,  etc.,  and  as  soon  as 
the  expectorated  material  has  become  dry  and  is  dissemi- 
nated in  the  form  of  dust  it  may  be  inhaled  by  any  num- 
ber of  people.  A  child,  again,  may  introduce  a  finger  con- 
taminated with  such  material  into  its  mouth  or  nose.  It 
is  also  possible  that  through  uncleanliness  bacilli  may  find 
their  way  into  food;  for  example,  a  child's  milk  may  be- 
come contaminated  in  course  of  preparation  by  a  mother 
suffering  from  tuberculosis.  The  bacilli  then  enter  the 
intestine  with  the  milk  and  thence  find  their  way  to  other 
organs.  The  inhalation  of  dried  and  pulverised  sputum 
may  lead  to  infection  by  the  same  channel,  for  a  portion 
of  the  inhaled  dust  lodges  in  the  mouth  or  pharynx,  is 
subsequently  swallowed,  and  thus  finds  its  way  into  the 
intestinal  canal.  The  bacilli  may  also  enter  the  body 
directly  from  the  pharynx,  especially  through  the  tonsils. 
Tuberculosis  is  rarely  transmitted  by  wounds.  The  trans- 
mission of  acute  pneumonia  by  direct  infection  from  per- 
son to  person  is  hardly  known  to  occur,  but  when  the 
micrococci  which  cause  this  disease  obtain  lodgment  on 


62  Heredity,  Disease  and  Human  Evolution 

the  walls  or  in  the  flooring  of  the  patient 's  room  they  may 
retain  their  vitality  for  a  considerable  period  .and  may 
ultimately  find  their  way  into  the  body  of  another  indi- 
vidual. Such  prolonged  intervals  in  the  transmission  of 
infection  are  possible  also  in  the  case  of  the  tubercle  and 
the  diphtheria  bacillus.  Direct  infection  is  observed  in 
cholera  and  typhoid  when  healthy  persons  handle  the  pa- 
tient's evacuations  in  a  careless  or  uncleanly  manner,  and 
infect  themselves  directly  or  through  the  instrumentality 
of  food  or  drink.  "Washerwomen,  also,  may  be  infected 
with  these  diseases,  when  handling  soiled  linen.  In  most 
cases,  however,  typhoid  and  cholera  are  transmitted 
through  the  instrumentality  of  water  into  which  the  excit' 
ing  causes  of  the  disease  have  found  their  way,  and  which 
is  subsequently  drunk  by  healthy  individuals.  It  often 
happens  that  the  contaminated  water  is  employed  to  wash 
milk  cans  or  other  utensils  in  which  milk  is  stored,  or  is 
used  to  dilute  milk,  which  is  thus  rendered  infective.  Dan- 
ger of  infection  also  arises  from  the  washing  of  vegetables, 
and  especially  of  salad,  in  germ-contaminated  water.  There 
are  other  infectious  diseases  in  which  the  method  of  trans- 
mission is  even  more  complicated.  The  intermediary  may 
be  another  animal,  in  which  the  infective  micro-organism 
is  also  able  to  live.  In  the  diffusion  of  bubonic  plague,  for 
example,  it  is  now  well  known  that  the  rat  plays  an  impor- 
tant part.  Malarial  fever  and  sleeping  sickness  are  diffused 
by  the  intermediation  of  certain  biting  insects.  These 
suck  up  the  blood  of  individuals  suffering  from  the  dis- 
eases in  question,  in  whom  the  blood  itself  contains  |;he 
living  organisms  that  cause  the  disease ;  and  after  the  or- 
ganisms have  undergone  certain  changes  in  the  body  of 
the  insect-host,  this  last  by  its  bite  inoculates  a  healthy 
individual  with  the  disease.  Animal  parasites  of  a  higher 
order,  such  as  the  filaria  met  with  in  the  tropics,  may  be 
transmitted  in  a  similar  way.  Every  one  knows  that  tape- 
worms and  trichinae  have  as  intermediate  hosts  certain 
animals  used  by  us  for  food  (cattle  and  swine),  and  that 


The  Significance  of  Diseases  to  Society    63 

the  parasite  is  transmitted  to  healthy  individuals  through 
the  ingestion  of  meat  containing  the  parasitic  worm. 

These  examples  may  suffice.  For  the  purposes  of  the 
present  book  it  is  unnecessary  to  give  a  more  detailed  ac- 
count of  the  methods  of  transmission.  All  that  we  are 
here  concerned  with  is  to  recall  to  the  reader's  memory 
how  extensive  and  manifold  are  the  possibilities  of  dis- 
semination of  such  diseases,  and  how  dangerous  in  conse- 
quence are  the  sick  to  their  healthy  associates.  It  is  hardly 
necessary  to  insist  upon  the  colossal  extension  which  may 
be  attained  by  such  diseases,  especially  tuberculosis,  dipli- 
theria,  measles,  scarlatina,  cholera,  typhoid,  bubonic 
plague,  smallpox,  etc.,  in  consequence  of  repeated  trans- 
mission from  person  to  person.  The  fact  is  always  before 
our  eyes  in  recurrent  epidemics  of  such  diseases. 


CHAPTER  VI 

THE  SIGNIFICANCE  OF  DISEASES  TO  THE  OFFSPRING 

The  offspring  have  to  suffer  in  manifold  ways  from  tlie 
effects  of  the  diseases  of  the  parents,  and  in  part  also 
from  the  effects  of  those  of  earlier  direct  ancestors.  This 
matter  is  one  of  very  great  importance,  for  the  evolution, 
the  future,  of  the  human  race  depends  upon  its  off- 
spring. If  these  are  always  being  injured,  and  if  this  proc- 
ess continues  for  all  time,  there  is  little  hope  of  any  im- 
provement upon  present  conditions,  little  prospect  that 
the  human  race  will  ever  he  able  to  attain  to  a  higher  level 
of  average  well-being  and  happiness.  The  question  is  there- 
fore one  of  lively  interest  whether  the  infliction  of  injury 
on  the  offspring  by  the  diseases  of  their  progenitors  will 
necessarily  continue  through  all  future  ages,  or  whether 
it  will  be  possible  to  diminish  or  even  to  abolish  these 
injurious  consequences.  To  enable  us  to  answer  this  ques- 
tion we  must  first  consider  the  various  eventualities  that 
may  lead  to  injury  to  children  and  children's  children. 


A.    Injuries  Inflicted  upon  Children  by  Bad  Upbring- 
ing AND  Education 

Whilst  brief  and  transient  illnesses  affecting  the  parents 
cannot  react  unfavourably  to  a  notable  extent  upon  the 
upbringing  of  their  children,  illnesses  of  long  duration 
necessarily  prove  injurious  in  many  ways.  Sick  parents 
cannot  take  proper  care  of  their  children,  and  may  be 
forced  to  neglect  them  altogether;  the  children  are  then 

64 


Significance  of  Diseases  to  Offspring     65 

deprived  of  parental  influence  and  instruction,  and  in  most 
cases  no  substitute  is  provided  to  compensate  for  this  loss. 
Undoubtedly,  not  all  children  will  be  seriously  injured 
thereby.  Upon  those  whose  inherited  tendencies  are  good, 
the  illness  of  the  parents  may  occasionally  exercise  a  good 
educative  influence.  There  can  be  no  doubt,  however,  that 
as  a  rule  the  lack  of  parental  instruction  has  injurious 
results.  School  cannot  provide  a  substitute  for  parental 
care,  especially  in  view  of  the  fact  that  schooling  does  not 
usually  begin  before  the  sixth  year  of  life. 

In  such  cases  the  defective  upbringing  takes  the  form, 
first  of  all,  of  an  inadequacy  of  mental  and  especially  of 
ethical  training.  Sick  parents,  and  above  all  parents  whose 
own  moral  level  is  a  low  one,  are  incompetent  to  care  for 
the  moral  development  of  their  children,  and  may  even 
favour  the  moral  degeneration  of  these  by  bad  teaching 
and  example.  It  must  not  be  forgotten,  moreover,  that 
the  children  of  such  sick  parents  are  apt,  by  inheritance, 
to  start  in  life  with  a  defective  equipment,  a  question  soon 
to  be  considered;  but  it  is  obvious  that  there  will  be  a 
much  stronger  tendency  for  the  children  to  develop  along 
wrong  lines  when  the  parents  set  them  a  bad  example.  In 
families  addicted  to  crime  the  children  are  often  directly 
taught  theft,  lying,  etc.  It  is  well  known,  also,  that  such 
parents  often  deliberately  neglect  their  children,  and  even 
mutilate  them  in  various  ways,  in  order  to  arouse  pity,  and 
thus  extort  money  from  the  charitably  disposed. 

Of  no  less  importance  is  the  inadequacy  of  the  bodily 
care  provided  for  the  children  of  abnormal  parents.  Wlien 
the  mother  is  ill  the  child  is  often  badly  nourished  from 
very  early  days,  and  even  from  birth.  The  mother's  milk, 
the  child's  natural  food,  is  not  forthcoming,  and  the  child 
is  brought  up  on  cow's  milk  or  even  on  milk-substitutes. 
Failure  of  the  mother's  milk  occurs  in  many  serious  ill- 
nesses, such  as  severe  tuberculosis ;  but  incapacity  for  suck- 
ling may  also  depend  upon  a  defective  development  of 
the  mammary  glands,  which  may  be  inherited,  and  which 


66  Heredity,  Disease  and  Human  Evolution 

by  some  is  believed  to  be  a  consequence  of  the  excessive 
use  of  alcohol  on  the  part  of  the  parents  or  even  the  grand- 
parents of  the  woman  who  is  incompetent  for  lactation. 
This  question  will  be  considered  later. 

In  many  cases,  however,  the  failure  to  suckle  the  infant 
is  not  due  to  the  mother's  defective  physical  development, 
but  to  the  fact  that  her  mental  disposition  is  a  bad  one. 
Often  a  woman  does  not  wish  to  suckle  her  child,  because 
of  the  inconveniences  entailed.  Here  we  have  to  do  with 
individuals  of  inferior  value  who  prefer  their  own  comfort 
to  the  well-being  of  their  children.  The  disastrous  results 
of  the  artificial  feeding  of  children  are  continually  being 
emphasised  by  medical  science  and  confirmed  by  medical 
experience.  Artificial  feeding  is  chiefly  to  blame  for  the 
tragic  extent  of  infantile  mortality,  for  the  fact  that  from 
20  to  30  per  cent,  of  all  children  born  succumb  during 
the  first  year  of  life.  Let  me  repeat,  that  of  100  children 
born,  as  many  as  30,  and  here  and  there  an  even  larger 
number,  die  in  earliest  infancy.  How  much  distress  and 
misery,  how  much  heedlessness  and  frivolity,  underlie  these 
figures!  How  great,  too,  is  the  loss  of  capital.  It  has  been 
calculated  that  for  every  one  of  these  children  there  has 
been  expended  250  dollars  of  national  property.  The  total 
w^aste  involved  will  become  evident  when  we  remember  that 
year  after  year  in  the  German  Empire  alone  250,000  chil- 
dren die  during  the  first  year  of  life. 

This  enormous  infantile  mortality,  which  is  such  a  scan- 
dal to  our  civilisation,  is  mainly  dependent  upon  defective 
or  erroneous  nutrition,  and  this  in  turn  comes  chiefly  when 
the  mother  cannot  or  will  not  suckle  her  child.  Mother's 
milk  is  the  most  natural  food  for  the  infant.  Cow's  milk, 
however  carefully  prepared,  can  never  be  a  perfect  substi- 
tute, though  it  is  the  best  available.  And  in  this  domain 
of  infant  feeding  what  sins  are  committed  in  the  giving 
of  improperly  prepared  cow's  milk,  or  in  feeding  infants 
from  foods  from  which  milk  is  absent.  No  doubt  this 
often  arises  from  poverty,  where  the  means  do  not  per- 


Significance  of  Diseases  to  Offspring     67 

mit  of  the  purchase  of  enough  milk  for  the  child ;  but  this 
poverty,  in  turn,  is  frequently  the  outcome  of  illness  in 
the  parents  whereby  their  earning  capacity  is  impaired. 
Nor  is  poverty  the  only  cause.  Ignorance,  erroneous  teach- 
ing, an  obstinate  adhesion  to  tradition,  and  superstition,  all 
play  their  part,  and  these  are  conditions  dependent  upon 
the  fact  that  the  mental  constitution  of  the  parents  is 
below  par  value,  and  often  definitely  diseased. 

It  may  be  admitted  that  of  late  years  there  has  been 
some  improvement,  that  there  has  been  a  decline  in  infan- 
tile mortality.  This  improvement,  however,  does  not  de- 
pend so  much  upon  the  provision  of  better  conditions  by 
parents,  as  upon  advance  in  medical  skill ;  upon  the  munici- 
palities, where  these  provide  for  the  supply  of  sufficient 
quantities  of  properly  prepared  milk  at  the  lowest  possible 
price ;  and  upon  the  state,  in  so  far  as  this  has  taken  steps 
to  secure  an  improvement  in  sanitary  conditions.  The 
morbid  dispositions  of  parents,  the  inferiority  of  their 
values,  persist  unchanged. 

The  injurious  effects  of  illness  are  not  confined  to  the 
first  year  of  the  child's  life.  Numerous  children  who  sur- 
vive the  year  of  infancy  subsequently  succumb  to  the 
effects  of  bad  nutrition,  while  others  are  thereby  perma- 
nently weakened. 

In  certain  districts,  moreover,  alcohol  is  given  to  chil- 
dren, chiefly  in  the  form  of  beer.  The  parents,  who  are 
themselves  addicted  to  the  excessive  use  of  beer,  regard 
it  as  a  suitable  and  strengthening  article  of  diet  for  their 
children.  We  cannot  go  so  far  as  to  say  that  all  the  par- 
ents who  give  their  children  alcohol  are  themselves  dis- 
eased in  the  strict  sense  of  the  term.  To  a  large  extent, 
certainly,  we  are  here  concerned  merely  with  the  thought- 
less adhesion  to  a  traditional  local  practice.  Yet  it  must 
be  admitted  that  such  parents  are  necessarily  below  par 
value  in  the  matter  of  intelligence,  for  otherwise  they 
could  not  fail  to  recognise  that  a  beverage  capable  of  pro- 
ducing intoxication  in  the  adult  must  be  unsuitable  for  th(^ 


68  Heredity,  Disease  and  Human  Evolution 

immature  organism.  Hence  in  this  ease  also  the  injury 
to  the  children  is  dependent  upon  the  morbid  constitution 
of  the  parents.  [Fortunately  Anglo-Saxon  children  are 
not  poisoned  by  beer ;  but  how  often  do  we  habituate  them 
to  the  use  of  tea  and  coffee! — W.  J.  R.] 

Disadvantageous  in  manifold  ways  as  is  the  illness  of  the 
parents  to  the  upbringing  of  the  children,  the  death  of 
father,  or  mother,  or  both,  is  apt  to  prove  even  more  dis- 
astrous. The  father's  death  removes  the  breadwinner,  and 
the  poverty  of  the  family  then  often  becomes  extreme.  By 
the  death  of  the  mother,  the  developmental  chances  of  little 
children  are  especially  impaired.  It  is  quite  true  that  the 
death  of  parents  who  are  mentally  disordered  may  be  ad- 
vantageous for  the  ethical  upbringing  of  tlieir  offspring,  if 
the  result  is  that  the  children  are  now  brought  up  in 
other  families  or  in  suitable  orphanages.  Apart  from  these 
exceptional  cases,  we  cannot  fail  to  recognise  that  the 
lack  of  parental  training  is  always  disadvantageous  to 
children. 

B.    Appearance  of  Diseases  in  the  Offspring.  Heredity 

In  the  previous  section  we  gave  an  exposition  of  the 
disadvantages  from  which  children  suffer  when  the  parents 
are  incapacitated,  owing  to  illness,  from  giving  proper 
attention  to  the  bodily  and  mental  upbringing  of  their 
offspring.  In  such  cases  there  often  results  a  serious  im- 
pairment of  the  proper  course  of  development,  the  children 
not  infrequently  becoming  ill  both  mentally  and  physically. 
A  no  less  serious  danger  arises  because  the  illnesses  of  the 
parents  may  affect  the  offspring,  not  only  or  not  mainly 
through  defective  upbringing,  but  by  the  direct  transmis- 
sion of  disease. 

Such  transmission  is  facilitated,  in  the  case  of  diseases 
caused  by  micro-organisms,  by  the  close  relationships  be- 
tween parent  and  child,  in  consequence  of  which  infection 
very  readily  results.    This  is  seen,  for  example,  in  the  case 


Significance  of  Diseases  to  Offspring     69 

of  tuberculosis.  Reference  has  previously  been  made  to  \ 
the  fact  that  one  of  the  greatest  dangers  in  this  connexion 
is  that  the  mother  may  infect  the  child  directly  through 
the  expectoration  of  tubercle  bacilli,  or  indirectly  through 
contaminating  the  child's  milk  or  other  food,  and  also  that 
the  children  may  infect  themselves  through  the  handling 
of  dirty  objects,  contaminated  by  expectorated  bacilli. 

The  transmission  of  infectious  disease  from  parent  to 
offspring  may,  however,  also  be  effected  before  birth.  In 
this  connexion  there  are  two  possibilities.  First  of  all,  the 
disease-producing  influence  may  affect  the  developing  child 
within  the  mother's  womb,  and,  in  the  second  place,  it  may 
operate  upon  the  so-called  germinal  cells,  that  is  to  say 
upon  ovum  or  spermatazoon  before  the  occurrence  of  that 
union  between  these  cells  which  is  known  as  fertilisation. 
This  latter  possibility  is  of  especial  interest  and  importance 
because  we  are  here  concerned  with  an  injury,  not  merely 
to  the  particular  individual  produced  by  the  union  of  the 
germinal  cells  thus  affected,  but  also  with  one  of  the  re- 
moter offspring,  perhaps  for  many  generations.  For  a 
disease  of  the  germinal  cells  is  transmitted  to  the  germinal 
cells  of  the  developing  child,  and  therewith  to  the  indi- 
viduals that  will  be  produced  out  of  these  germinal  cells 
in  a  subsequent  generation.  This  is  what  we  mean  by 
inheritance. 

Owing  to  the  enormous  importance  of  this  matter  to 
human  evolution,  its  detailed  consideration  is  essential. 
First  of  all  we  shall  give  a  general  description  of  the 
manner  in  which  diseases  of  the  parents  may  influence  the 
erminal  cells  and  the  individuals  produced  out  of  these. 

Let  us  begin  with  the  germinal  cells.  In  the  diseased 
*body,  these  may  be  affected  by  many  injurious  influences. 
When  any  poison  invades  the  parental  organism  and  makes 
this  ill,  the  poison  may  have  an  effect  on  the  germinal 
cells  just  as  upon  any  other  cells,  and  may  induce  changes 
in  these.  If  a  germinal  cell  thus  rendered  abnormal  now 
unites  in  the  process  of  fertilisation  with  a  germinal  cell 


70  Heredity,  Disease  and  Human  Evolution 

of  the  opposite  sex,  the  alterations  that  have  been  induced 
may  take  effect  within  the  developing  ovum,  giving  rise  to 
changes  varying  according  to  the  nature  of  the  poison  and 
to  the  specific  effect  it  has  exercised  upon  the  germinal 
cell,  but  which  may  take  the  form  of  deviations  from  the 
normal  structure  now  in  one  organ  and  now  in  another, 
inducing  disease,  perhaps  in  childhood,  perhaps  later  in 
life.  Inasmuch  as  we  are  forced  to  conceive  that  in  some 
way  or  other  the  germinal  cells  already  contain  the  rudi- 
ments of  the  various  bodily  organs,  these  latter  may  be 
individually  injured.  For  example,  if  the  rudiment  of  the 
brain  suffers,  mental  disorder  will  subsequently  result. 

But  poisons  introduced  from  without  are  not  the  only 
ones  that  may  affect  the  germinal  cells.  The  poisons  that 
act  in  this  way  may  also  originate  within  the  body,  and 
here  we  think  especially  of  the  working  of  the  micro-organ- 
isms which  produce  the  infectious  diseases.  For  the  dis- 
ease-producing activities  of  these  organisms  depend  mainly 
upon  the  toxins  that  they  manufacture ;  mingling  with  the 
blood  these  toxins  find  their  way  to  the  reproductive 
glands.  In  the  second  place,  however,  there  are  poisons 
that  arise  spontaneously  in  the  diseased  body,  as  when 
altered  organs,  such  as  the  kidney,  fail  to  eliminate  sub- 
stances which  are  normally  eliminated  in  the  urine.  Being 
retained  in  the  body,  these  substances  act  as  poisons.  It 
may  also  happen  that  the  affected  organs,  whose  normal 
task  it  is  to  render  certain  products  of  tissue-change  harm- 
less, are  no  longer  able  to  do  their  duty  in  this  respect. 
Finally  it  may  happen  that  the  altered  organs,  whose 
proper  function  it  is  to  provide  certain  substances  essential 
to  the  normal  body,  produce  substances  of  altered  compo- 
sition which  exercise  an  injurious  influence. 
^KA.  great  deal  more  will  have  to  be  said  in  this  book  of 
these  various  possibilities  of  germinal  intoxication  in  our 
discussion  of  the  problems  of  the  inheritance  of  disease. 

It  is  also  necessary  to  point  out  that  when  the  parental 
organism  is  greatly  weakened  by  disease,  the   germinal 


Significance  of  Diseases  to  Offspring     71 

cells  may  suffer  from  an  insufficient  supply  of  nutriment. 

In  addition  to  diseases  in  the  narrower  sense  of  the 
term,  there  may  arise  in  the  offspring  various  conditions 
which,  though  they  cannot  themselves  be  regarded  as  neces- 
sarily morbid  states,  yet  render  the  organism  unduly  liable 
to  the  onset  of  disease. 

Certain  infectious  diseases  affect  the  germinal  cells  in  a 
special  way,  inasmuch  as  the  micro-organisms  which  are 
the  exciting  causes  of  the  diseases  in  question  invade  the 
germinal  cells  without  depriving  them  of  their  fertilising 
power  and  without  interfering  with  the  earliest  stages 
of  subsequent  development.  When,  at  a  later  stage,  the 
organisms  undergo  multiplication  in  the  gi'owing  individ- 
uals they  may  then  give  rise  to  the  changes  characteristic 
of  their  action.  In  the  disease  of  silk-worms  known  as 
pebrine,  for  example,  we  are  able  to  observe  under  the 
microscope  that  the  exciting  cause  is  present  in  the  eggs 
of  the  insect,  being  thus  transmitted  to  the  new  generation 
of  silk-worms  and  in  them  reproducing  the  disease. 

As  far  as  human  beings  are  concerned,  this  mode  of 
germinal  infection  has  to  be  considered,  above  all,  in  the 
case  of  tuberculosis.  The  matter  has  been  greatly  dis- 
cussed whether  tubercle  bacilli  invade  the  germinal  ceUs, 
but  investigators  are  now  generally  agreed  that  if  this  ever 
does  occur  in  man  it  is  extremely  rare.  No  one  has  yet  suc- 
ceeded in  demonstrating  under  the  microscope  the  presence 
of  tubercle  bacilli  in  human  ova  or  spermatozoa.  We 
learn,  however,  from  experiments  on  animals  that  the  inva- 
sion of  the  germinal  cells  by  these  organisms  is  possible. 
In  birds,  tubercle  bacilli  have  been  introduced  into  the 
peritoneal  cavity,  where  they  come  into  contact  with  the 
ova.  It  has  been  shown  in  these  cases  that  the  ova  can  be 
fertilised  and  that  the  eggs  will  develop,  but  that  the  chick- 
ens are  tuberculous  when  hatched.  A  similar  process  is 
conceivable  in  human  beings,  for  in  cases  of  peritoneal 
tuberculosis  in  women  the  bacilli  might  invade  the  ovum. 
As  a  rule,  however,  in  this  disease,  the  woman  is  so  ill 


72  Heredity,  Disease  and  Human  Evolution 

that  fertilisation  does  not  occur.  It  follows  that  such  in- 
fection of  the  ova  must  be  extremely  rare  in  human  beings. 
In  the  semen  of  tuberculous  men  bacilli  are  so  rarely  found 
that  the  possibility  that  tubercle  bacilli  might  enter  the 
ovum  in  company  with  the  spermatazoon  in  the  process 
of  fertilisation  is  extremely  remote.  If  the  male  repro- 
ductive glands  are  actually  affected  with  tuberculosis,  so 
that  they  contain  large  quantities  of  bacilli,  the  danger  of 
transmission  to  the  offspring  is  inconsiderable,  for  the  rea- 
son that  the  changes  resulting  from  the  disease  commonly 
prevent  the  formation  or  at  least  the  evacuation  of  the 
semen,  and  therewith  render  fertilisation  impossible. 

Less  improbable  than  infection  of  the  ovum  by  bacilli 
introduced  with  the  semen  is  the  occurrence  of  infection 
in  this  way,  that  the  bacilli  thus  introduced  into  the  uterus 
may  sooner  or  later,  but  after  fertilisation,  infect  the 
developing  embryo.  Certain  experiments  on  animals  indi- 
cate 'that  this  is  possible,  but  the  occurrence  is  altogether 
exceptional. 

Syphilis  is  another  disease  in  which  the  possibility  of 
germinal  infection  has  to  be  considered.  In  the  case  of 
this  disease  the  general  assumption  used  to  be  that  the 
transmission  of  the  exciting  cause  was  frequently  effected 
by  means  of  the  spermatozoa  of  syphilitic  fathers.  Of  late 
years  another  view  has  gained  ground,  and  it  is  now  re- 
garded as  more  probable  that  the  man  first  infects  the 
woman  and  that  she  subsequently  infects  the  developing 
infant  in  the  manner  shortly  to  be  described. 

This  is  all  we  have  to  say  concerning  injurious  influences 
exercised  upon  the  germinal  cells  by  illness  in  the  parents. 
We  must  now  turn  to  consider  the  injuries  to  which  the 
child  is  exposed  in  the  course  of  its  development  within 
the  mother's  body,  in  consequence  of  disease  with  which 
the  mother  is  affected  at  the  time.  In  this  case,  also, 
several  possibilities  have  to  be  taken  into  account. 

One  source  of  injury  may  be  found  in  the  fact  that 
the  embryo  is  nourished  by  the  mother  through  the  inter- 


Significance  of  Diseases  to  Offspring     73 

mediation  of  tlie  placenta.  Substances  in  solution  pass 
from  the  maternal  blood  into  that  of  the  child.  If  the 
mother's  blood  contains  certain  poisons,  these  may  pass 
into  the  child's  blood  by  way  of  the  placenta,  just  like  the 
normal  nutritive  materials,  making  the  child  ill  or  even 
leading  to  its  death.  Among  such  poisons,  alcohol  must 
be  mentioned,  although  we  know  less  abuut  its  influence 
upon  the  embryo  than  we  do  about  its  significance  in  rela- 
tion to  the  germinal  cells.  The  other  poisons  mentioned 
above  may  also  prove  injurious  to  the  developing  child. 

There  is  also  the  possibility  that  when  the  mother  is  suf- 
fering from  infectious  disease  the  exciting  causes  of  this 
disease  may  invade  the  embryo,  and  this  chiefly  by  way 
of  the  placenta.  This  may  happen  in  the  case  of  tubercu- 
losis, though  perhaps  this  method  of  infection  is  not  of 
frequent  occurrence.  We  know,  however,  that  the  placenta 
is  not  rarely  affected  by  tuberculous  processes,  and  that 
bacilli  are,  of  course,  present  in  the  lesions.  It  is  pos- 
sible that  these  bacilli  may  invade  the  embryo.  The  more  j 
serious  the  disease  in  the  mother,  the  more  numerous  the  \ 
bacilli  in  the  placenta,  the  more  readily  will  the  child  | 
become  infected.  In  those  cases,  for  example,  in  which 
the  mother  dies  at  the  end  of  pregnancy  or  during  parturi- 
tion from  a  rapid  tuberculosis,  we  are  often  able  to  dem- 
onstrate the  abundant  presence  of  bacilli  in  the  body  of 
the  infant.  Where  the  mother's  tuberculosis  is  less  severe 
and  the  child  is  still-born  or  dies  shortly  after  birth,  we 
are  sometimes  able  to  demonstrate  the  presence  of  tuber- 
culous foci.  If  in  children  dying  a  few  weeks  or  months 
after  birth  we  find  extensive  tuberculosis,  we  are  justified 
in  assuming  that  the  disease  already  existed  at  the  time  of 
birth  and  arose  in  the  manner  above  described.  In  gen- 
eral, instances  of  congenital  tuberculosis  constitute  no 
more  than  a  trifling  percentage  of  all  cases  of  this  disease. 
It  has,  however,  to  be  admitted  that  some  authorities  are 
of  opinion  that  congenital  tuberculosis  is  of  comparatively 
frequent  occurrence. 


74  Heredity,  Disease  and  Human  Evolution 

Apart  from  tuberculosis  there  are  in  practice  not  many 
diseases  which  have  to  be  considered  in  connexion  with 
the  possibility  of  infection  through  the  placenta.  Such 
transmission  has  been  observed  in  the  case  of  anthrax, 
typhoid,  small-pox,  scarlatina,  measles,  acute  pneumonia, 
wound-infections,  erysipelas.  The  three  diseases  last  men- 
tioned are  o:!^  especial  interest  because  they  are  responsible 
for  the  occurrence  in  the  embryo  of  inflammations  of  the 
valves  of  the  heart.    But  these  affections  are  rare. 

Injuries  to  the  child  within  the  body  of  the  mother  may 
also  arise  in  consequence  of  pathological  conditions  in  the 
uterus.  There  may  be  insufficient  space  for  the  child ;  the 
uterus  may  be  displaced ;  the  umbilical  cord  may  surround 
some  part  of  the  embryo,  especially  one  of  the  extremities ; 
the  membranes  may  adhere  to  the  surface  of  the  child's 
body.  In  this  way  there  arise  various  disturbances  of 
development,  more  or  less  serious  malformations. 

This,  however,  is  not  the  only  way  in  which  malforma- 
tions arise.  Many  of  these  are  dependent  upon  diseases 
of  the  germ,  arising  under  conditions  to  which  reference 
has  already  been  made,  transmitted,  for  instance,  from 
previous  generations.  Many  malformations  are  transmis- 
sible by  inheritance;  the  changes  in  the  germinal  cells  by 
which  they  are  induced  may  have  originated  in  the  grand- 
parents or  great  grandparents,  or  even  in  remoter  ances- 
tors. This  question  will  be  more  closely  considered  when 
we  come  to  deal  with  the  inheritance  of  diseases.  But  first 
we  have  to  occupy  ourselves  with  the  general  principles  of 
inheritance,  for  without  a  knowledge  of  these  it  is  impos- 
sible to  understand  the  process  of  the  inheritance  of  dis- 
ease. 

For,  notwithstanding  numerous  peculiarities  by  which 
the  inheritance  of  morbid  states  is  distinguished,  this  pecu- 
liar phenomenon  is  merely  a  part  of  the  general  phenome- 
na of  heredity,  and  the  former  cannot  be  fruitfully  consid- 
ered except  in  connexion  with  the  latter.  Consequently, 
before  we  discuss  the  hereditary  transmission  of  diseases, 


Significance  of  Diseases  to  Offspring     75 

we  must  inform  ourselves  as  to  the  general  conditions  of 
heredity,  as  to  its  anatomical  basis,  and  as  to  other  matters. 

1.     General  Phenomena  of  Herediiif 

"We  know  from  ever-recurrent  experience  that  no  one  liv- 
ing human  being  is  perfectly  similar  in  all  details  to  an- 
other individual  of  the  same  species.  Every  plant,  every 
animal,  differs  from  its  fellows,  and  these  differences  exist 
not  only  as  regards  the  individual  as  a  whole  but  also  as 
regards  all  its  parts.  No  leaf  corresponds  in  every  char- 
acteristic with  any  of  the  innumerable  other  leaves  of 
plants  of  the  same  species.  It  is  the  same  with  human 
beings.  Not  one  of  us  can  be  exchanged  for  any  other, 
and  even  if  in  exceptional  cases  there  exists  an  intimate 
resemblance  between  two  individuals,  a  close  examination 
soon  shows  that  differences  exist  both  in  mind  and  body. 
We  may  go  so  far  as  to  maintain  that  two  absolutely  simi- 
lar men  never  have  existed  in  the  past  and  never  will 
exist  in  the  future.  The  number  of  individual  human  char- 
acteristics is  so  great  as  to  render  it  impossible  that  two 
human  beings  should  ever  exhibit  the  same  combination, 
the  same  number,  and  the  same  arrangement,  for  all  the 
myriads  of  individual  characteristics. 

Thus  every  human  being  is  a  peculiar  individual  whose 
perfect  counterpart  can  never  be  found.  The  explanation 
of  this  is  not  that  all  human  beings  start  alike,  and  that 
they  only  become  different  subsequently  because  the  vital 
conditions,  the  environmental  influences  that  affect  us, 
which  are  never  exactly  the  same  for  any  two  living  beings, 
have  evoked  the  various  individual  peculiarities  out  of 
primarily  homogeneous  rudiments.  For  the  most  part  nu- 
tritive, housing,  and  climatic  conditions,  and  the  other 
environmental  conditions  surrounding  our  youth,  wherein 
all  these  differences  become  manifest,  are  similar  to  such 
a  degree,  that  it  would  be  impossible  for  the  comparatively 
slight  differences  that  do  exist  in  these  conditions  to  give 


76  Heredity,  Disease  and  Human  Evolution 

rise  to  the  unending  multiformity  in  the  personal  charac- 
teristics of  mankind.  There  is  no  other  possibility  than 
that  individual  human  beings  are  different  from  the  start, 
that  they  differ  as  to  their  rudiments.  No  one  really  ques- 
tions this.  Yet  the  most  markedly  developed  individuality 
is  far  from  being  rigid  and  unalterable.  Just  as  the 
physical  characteristics  undergo  gradual  transformation  in 
the  course  of  life,  so  also  there  ensues  a  change  in  the 
mental  peculiarities;  and  this  does  not  occur  only  from 
within  outwards,  for  reasons  dependent  simply  upon  the 
spontaneous  development  of  the  individual  as  age  advances, 
but  it  also  arises  as  an  outcome  of  the  influence  of  numerous 
external  conditions.  Not  one  of  us  doubts  that  if  the  cir- 
cumstances of  his  life  had  been  different,  his  development 
would  have  taken  a  different  course,  above  all  as  far  as 
mental  characteristics  are  concerned.  We  can  well  con- 
ceive that  one  whose  upbringing  has  led  him  to  exercise 
his  faculties  in  the  domain  of  pure  science  might,  under 
other  conditions,  if  he  had  grown  up  in  another  family, 
have  developed  a  remarkable  aptitude  for  music.  Such 
possibilities  are  innumerable.  But  would  such  changes  in 
his  activities  seriously  alter  the  individual?  Would  a 
different  individual  thus  be  created,  in  whom  the  other 
individuality  could  no  longer  be  recognised?  Obviously, 
nothing  of  the  kind  could  take  place.  All  that  happens 
in  such  cases  is  merely  that  another  side  of  the  individu- 
ality becomes  conspicuous  than  the  one  which,  under 
other  conditions,  would  have  been  specially  developed. 

Thus  the  only  change  that  has  been  effected  is  one  which 
concerns  the  mutual  relationships  between  the  individual 
characteristics.  No  new  element  has  been  introduced.  All 
that  has  happened  is  that  one  or  other  side  of  the  indi- 
vidual has  been  rendered  more  conspicuous  than  would 
have  been  the  case  under  normal  conditions. 

To  express  the  matter  in  other  terms,  we  have  in  such 
cases  adapted  ourselves  to  the  changed  external  influences ; 


Significance  of  Diseases  to  Offspring     77 

we  have  brought  our  faculties  into  harmony  with  the  de- 
mands made  upon  us. 

But  this  capacity  for  adaptation  to  special  vital  condi- 
tions is  just  as  much  an  inborn  characteristic  of  living 
beings  as  are  the  innumerable  individual  differences  of 
which  we  have  been  speaking,  and  upon  whose  modifia- 
bility  within  certain  limits  we  have  been  enlarging. 

All  these  peculiarities,  including  the  power  of  adapta- 
tion, attach  to  the  individual  and  endow  him  with  his  char- 
acteristic quality,  make  up  his  individuality.  But  they  are 
not  merely  attached  to  him ;  they  are  altogether  inseparable 
from  him.  We  cannot  conceive  of  any  human  being  as 
really  existing  utterly  devoid  of  individual  characteristics, 
of  one  who  would  be  simply  ' '  man, ' '  and  not  this,  that,  or 
the  other  particular  man  whose  double  is  nowhere  to  be 
found.  On  the  theoretical  plane  such  ideal  living  creatures 
can  be  constructed,  of  which  two  specimens  may  be  con- 
ceived to  resemble  one  another  in  every  possible  detail, 
but  in  the  concrete  no  such  specimens  exist.  Ideal  forms, 
like  those  created  by  Greek  sculpture,  have  no  actual  ex- 
istence. 

We  know  already,  and  shall  learn  more  precisely,  that  all 
living  creatures  are  the  offspring  of  pre-existent  living 
creatures,  originating  from  small  portions  of  the  parent 
organisms,  and  developing  out  of  the  growth  of  these 
portions,  which  pass  by  the  name  of  ova.  Upon  this  de- 
pends the  fact  that,  as  far  as  we  are  able  to  observe,  ani- 
mals and  plants  of  any  particular  species  are  always  the 
offspring  of  that  species,  that  man  is  always  born  from 
man.  In  the  ovum  out  of  which  the  living  creature  devel- 
ops there  already  exists  the  potentiality  of  the  individual 
subsequently  to  be  formed,  although  no  structural  evidence 
of  this  potentiality  can  be  discerned  by  our  senses.  The 
ovum  of  any  kind  of  animal  always  produces  an  animal 
of  this  kind,  and  however  much  we  may  alter  the  en- 
vironmental conditions  it  never  develops  into  a  living  crea- 
ture   with    characteristics    belonging   to    another   species. 


78  Heredity,  Disease  and  Human  Evolution 

From  the  human  ovum  there  invariably  develops  a  human 
being,  and  this  is  not  "man"  in  general,  but  a  peculiar 
and  individual  human  being  differentiated  from  all  others. 
It  follows  that  there  exist  in  the  ovum  the  rudiments,  not 
tnerely  of  the  general  peculiarities  which  distinguish  men 
as  men,  or  the  animals  of  any  other  species  as  such,  but 
also  the  rudiments  of  all  the  special  bodily  or  mental 
characteristics  by  which  the  individual  is  distinguished 
from  all  others  of  his  own  kind.  This  conclusion  is  not 
imposed  upon  us  solely  by  theoretical  considerations,  which 
show  us  that  no  other  possibility  is  conceivable  than  that 
all  these  innumerable  characteristics  should  be  potentially 
represented  in  the  ovum,  but  it  is  also  a  necessary  deduc- 
tion from  certain  observations  subsequently  to  be  described. 
If  this  is  so,  if  we  proceed  from  parts  of  our  parents, 
we  may  assume  that  the  developmental  possibilities  whose 
existence  in  the  germ  has  to  be  presupposed,  and  in  con- 
sequence of  which  the  individuals  subsequently  to  be 
formed  come  into  existence,  will  harmonise  with  the  quali- 
ties of  the  parents.  For  the  part  will  contain  no  other 
peculiarities  than  the  whole,  which  is  in  this  case  the  par- 
ental organism.  It  follows  that  the  children  will  possess 
the  same  characteristics  as  the  parents,  that  the  former 
will  resemble  the  latter.  This  is  precisely  what  we  under- 
stand by  heredity.  Heredity  is,  indeed,  often  conceived 
as  a  transmission  of  parental  qualities  to  the  offspring.  A 
detailed  examination  will  be  necessary  to  enable  us  to  de- 
termine whether  this  conception  is  really  accurate.  For 
the  present  we  shall  regard  the  term  heredity  as  merely 
an  expression  of  the  fact  that  offspring  resemble  parents 
through  the  intermediation  of  the  germinal  cells.  We  are 
careful  to  use  the  term  "resemble."  Heredity  never  re- 
sults in  a  complete  reproduction  of  qualities.  Parents 
and  children  are  distinguished  from  one  another  in  their 
characteristics  just  as  are  all  other  human  beings,  though 
there  is  more  resemblance  between  parents  and  children 
than  between  individuals  not  thus  related.    How  does  this 


Significance  of  Diseases  to  Offspring     79 

come  to  pass?  Under  the  conditions  with  which  we  are 
concerned  there  are  three  reasons. 

First  of  all  it  must  be  pointed  out  that  individual  human 
beings  may  experience,  through  the  influence  of  particular 
vital  conditions,  a  development  of  their  rudimentary  tend- 
encies different  from  that  which  has  occurred  in  the 
parents.  Attention  has  already  been  drawn  to  this  pos- 
sibility. Thereby  certain  divergences  between  offspring 
and  parent  may  be  induced.  We  must  repeat,  however, 
that  in  this  way  no  essential  difference  can  arise,  that  no 
new  characteristics  are  thereby  introduced  into  the  child's 
body;  all  that  can  happen  is  that  the  pre-existent  charac- 
teristics may  experience  a  greater  or  a  lesser  development. 

Secondly  we  have  to  consider  that  a  child  is  never  de- 
rived from  a  single  parent,  but  always  from  two,  and  that 
it  therefore  represents  an  admixture  of  the  peculiarities 
of  the  father  and  of  the  mother,  individuals  who  differ 
each  from  the  other.  By  this  admixture,  characteristics 
may  be  juxtaposed  in  the  children  which  exist  separately 
in  the  parents,  and  peculiarities  common  to  the  father  and 
the  mother  may,  owing  to  a  summation  of  effects,  attain 
an  especially  marked  development  in  the  child.  Upon  this, 
in  part,  depends  the  fact  that  in  children  certain  charac- 
teristics may  arise  to  all  appearance  spontaneously,  when 
such  characteristics  were  present  in  the  parents  only  to  a 
moderate  extent.  Other  qualities  may  restrict  one  an- 
other's development,  exercising  a  mutual  inhibition  so  that 
they  cease  to  be  noticeable.  Or,  again,  a  mingling  of  char- 
acteristics may  lead  to  the  appearance  of  some  quality 
which  was  non-existent  as  such  in  the  progenitors.  To 
give  an  example,  by  the  union  of  tendencies  to  the  pro- 
duction of  black  hair  and  of  fair  hair,  an  intermediate 
colouration  might  arise  in  the  children.  But  we  must  not 
overlook  that  the  cause  of  the  production  of  this  new  tint 
is  also  to  be  found  in  the  constitution  of  the  parental 
parts.  The  hair  of  intermediate  colouration  has  had  its 
existence  rendered  possible  because  of  the  pre-existence  in 


80  Heredity,  Disease  and  Human  Evolution 

the  respective  parents  of  tendencies  to  the  production  of 
black  hair  and  of  fair.  In  this  sense,  therefore,  we  may 
say  that  the  dissimilarity  of  the  child's  hair  is  itself  an 
inherited  quality,  but  we  are  accustomed  to  speak  of  hered- 
itary transmission  there  only  where  we  have  to  do  with 
resemblance  between  progenitors  and  offspring.  To  avoid 
confusion  we  shall  therefore  express  ourselves  in  other 
terms,  and  emphasise  the  fact  that  both  similarity  and 
dissimilarity  depend  upon  the  constitution  of  the  parental 
parts  from  which  the  offspring  proceed.  In  saying  this 
we  are  also  asserting  that,  inasmuch  as  there  is  no  way  in 
which  any  new  element  can  be  introduced  into  the  indi- 
vidual, all  the  rudiments  we  encounter  in  the  child  have 
pre-existed  in  one  way  or  another  in  the  parental  parts. 

While  we  are  thus  led  to  infer  that  the  offspring  may 
result  from  an  admixture  of  parental  tendencies,  we  must 
not  fail  to  insist  that  such  an  admixture  is  far  from  being 
the  rule.  The  separate  inheritance  of  characteristics  is 
much  commoner,  and  is  much  more  important  in  relation 
to  the  present  discussion.  Dark  hair  and  fair  hair,  and 
all  other  individual  characteristics,  generally  make  their 
appearance  distinctively  in  the  offspring,  and  not  as  an 
admixture  of  parental  characteristics.  This  matter  will  sub- 
sequently be  considered  in  further  detail. 

There  is  a  third  and  no  less  important  explanation  of 
the  frequent  differences  between  parents  and  children.  We 
find  in  the  children  the  characteristics,  not  only  of  par- 
ents, but  also  of  grandparents  and  of  remoter  ancestors, 
although  these  characteristics  have  not  been  exhibited  by 
the  immediate  progenitors.  It  is  thus  possible  that  quali- 
ties of  the  grandparents  existed  in  certain  parts  of  the 
parents,  that  is  to  say  in  the  maternal  ova  and  the  paternal 
spermatozoa  by  whose  union  the  children  were  formed, 
without  the  parents  themselves  having  manifested  the 
characteristics  in  question.  To  this  matter  we  shall  return. 
For  the  moment  we  shall  merely  indicate  that  the  condi- 
tion in  which  such  grandparental  qualities  exist  in  the 


Significance  of  Diseases  to  Offspring     81 

parents  is  known  as  one  of  latency.  This  means  that  in 
the  bodies  of  the  parents  the  qualities  in  question  are  in- 
effective and  concealed,  so  that  we  cannot  perceive  their 
existence.  When  a  child  resembles  a  grandparent  or  a 
yet  remoter  ancestor,  we  denote  the  phenomenon  by  the 
term  atavism..  It  is  necessary  to  lay  much  more  stress 
upon  such  inheritance  from  grandparents  and  remoter 
ancestors  than  is  commonly  done — at  any  rate  outside 
scientific  circles.  In  daily  life  when  people  speak  of  hered- 
ity they  generally  take  into  account  no  more  than  inher- 
itance from  father  and  mother.  Even  if  it  be  recognised 
that  grandchildren  may  resemble  their  grandparents  as 
well  as  their  parents,  the  possibility  of  inheritance  from 
great  grandparents  and  from  ancestors  yet  further  back 
in  the  scale  is  commonly  ignored.  Yet  it  is  essential  to 
recognise  the  existence  of  this  phenomenon,  for  then  only 
does  the  extraordinary  many-sidedness  of  the  individual, 
then  only  do  the  multiple  divergences  between  offspring 
and  parents,  become  fully  comprehensible.  We  have  now 
ascertained  the  reasons  for  the  existence  of  differences 
between  parents  and  children.  But  such  dissimilarity  is 
not  the  most  notable  feature  of  this  relationship,  for  the 
likeness  between  parents  and  offspring  is  far  more  obvious. 
It  is  of  resemblances  that  we  think  when  we  speak  of 
heredity.  They  are  our  leading  interest,  and  it  is  with 
them  that  we  must  be  chiefly  concerned. 

The  most  conspicuous  manifestation  of  heredity,  and  the 
one  therefore  whose  existence  can  most  easily  be  estab- 
lished, is  the  inheritance  of  body  peculiarities. 

When  we  speak  of  a  resemblance  between  parents  and 
children  we  think  especially  of  their  bodily  structure.  The 
stature,  the  colour  of  the  eyes  and  of  the  hair,  the  shape 
of  the  nose  and  of  the  ears,  and  many  other  physical  char- 
acteristics, are  often  transmitted  from  parent  to  child 
through  several  or  numerous  generations.  Every  one  will 
readily  recall  examples  of  this  in  his  own  family  or  in 
those  of  his  acquaintances.    Such  inheritance  often  extends 


82  Heredity,  Disease  and  Human  Evolution 

itself  to  quite  unimportant  details.  Thus  there  is  a  family 
in  which  a  white  lock  of  hair  has  been  transmitted  by 
inheritance  for  several  generations.  A  widely  celebrated 
instance  of  such  inheritance  is  that  of  the  strongly  devel- 
oped lower  lip  of  the  Hapsburg  family,  which  has  been 
transmitted  during  six  centuries,  persisting,  that  is  to  say, 
through  about  18  generations.  The  inheritance  of  mental 
peculiarities  is  less  easy  to  establish  than  that  of  physical. 
This  is  readily  comprehensible,  seeing  that  mental  capaci- 
ties are  not  transmitted  in  a  fully  developed  state.  It 
is  only  the  rudiments  of  the  mental  functions  that  are 
inherited.  The  functions  gradually  develop  at  a  later  date 
upon  the  foundation  of  these  rudiments,  which  are  often 
quite  unnoticeable  in  the  child. 

There  can,  however,  be  no  doubt  that  such  rudiments 
are  really  transmitted  by  inheritance,  and  that  they  do 
not  originate  de  novo  in  the  developing  organism.  To 
some  degree  the  mental  capacities  belong  to  man  as  such. 
As  members  of  the  human  species,  individuals  are  distin- 
guished by  particular  mental  tendencies,  which  are  con- 
tinually retransmitted  from  parents  to  offspring.  Man  as 
man  is  just  as  definitely  distinguished  by  mental  as  by 
bodily  characteristics.  But  the  development  and  the  oc- 
currence of  such  qualities  vary  greatly  in  different  indi- 
viduals, and  consequently  inheritance,  outside  the  gen- 
eral lines  of  its  action,  manifests  itself  in  this  way,  that 
parents  and  offspring  resemble  one  another  in  respect  of 
the  strength  and  combination  of  the  individual  tendencies. 

De  Candolle  made  a  remarkable  investigation  on  this 
point.  He  took  note  of  the  distinctive  characteristics  ex- 
hibited by  sixty  men,  and  then  examined  their  sons.  He 
established  that  90  per  cent,  of  the  qualities  were  common 
to  fathers  and  sons,  whilst  as  regards  the  remaining  10 
per  cent,  of  the  qualities,  these  were  either  common  to  sons 
and  grandparents,  or  were  explicable  on  the  ground  of  the 
above-deseribed  admixture  of  the  parental  qualities. 

Heredity  displays  itself  in  a  more  characteristic  way 


Significance  of  Diseases  to  Offspring     83 

when  we  have  to  do  with  very  peculiar  or  striking  mental 
qualities. 

We  all  know,  and  especially  every  one  of  us  has  learned 
at  school,  that  the  inborn  tendencies  characteristic  of 
human  beings  are  extraordinarily  diverse.  We  continually 
encounter  children  who  appear  to  possess  exceptional  en- 
dowments in  one  direction  or  another,  who  exhibit  a  re- 
markable capacity  for  mathematics,  for  example,  for  music, 
painting,  or  poetry.  Galton  established  this  in  the  course 
of  a  statistical  investigation  made  in  an  English  school, 
having  examined  during  two  years  the  mathematical  apti- 
tudes of  the  pupils  of  the  same  class  growing  up  under 
like  conditions.  He  showed  that  the  great  majority  pos- 
sessed only  a  moderate  mathematical  faculty,  that  a  smaller 
proportion  were  somewhat  better  equipped  in  this  respect, 
that  a  few  only  exhibited  a  high  development  of  the  fac- 
ulty, while  one  altogether  outdistanced  all  the  rest. 

The  most  remarkable  instances  of  exceptional  develop- 
ment of  inherited  faculty  are  met  with  in  the  so-called 
infant  prodigies.  I  need  merely  recall  that  Mozart's  per- 
formances were  astounding  even  in  early  youth.  Indeed, 
it  is  especially  in  the  case  of  music  that  such  early  devel- 
opment of  faculty  is  a  familiar  experience ;  and  we  are 
continually  meeting  fresh  examples  of  phenomenally  musi- 
cal children.  A  similar  early  development  occurs  in  manj'' 
mathematicians.  Gauss  says  jestingly  of  himself  that  he 
could  calculate  before  he  could  speak.  I  may  also  men- 
tion the  physicist  Thomson  (Lord  Kelvin),  who  began  to 
attend  the  university  at  ten.  It  is  not  necessary  to  give 
any  additional  instances. 

Such  altogether  exceptional  development  of  faculty  is 
characterised  especially  by  this,  that  the  faculty  finds 
expression  even  when  the  external  conditions  are  unfav- 
ourable, when  all  kinds  of  obstacles  are  imposed,  when 
the  individuals  thus  endowed  have  to  contend  with  pov- 
erty, or  when  the  parents  endeavour  by  threats  or  other- 
wise to  interfere  with  a  special  bent.    We  often  hear  how 


84  Heredity,  Disease  and  Human  Evolution 

great  men  have  had  to  overcome  such  obstacles.  It  is 
reported,  for  instance,  that  one  of  the  Bernoulli,  a  mem- 
ber of  the  celebrated  family  of  mathematicians,  was  con- 
tinually being  blamed  by  his  parents  for  his  devotion  to 
his  chosen  science,  while  another  member  of  the  family 
had  to  work  in  secret.  The  father  of  Pascal,  the  celebrated 
mathematician,  threw  many  obstacles  in  the  way  of  his 
son's  studies,  regarding  them  as  injurious  to  the  lad's 
health. 

Whilst  these  strongly-marked  endowments  cannot  be 
suppressed,  we  often  see,  on  the  other  hand,  how,  despite 
the  best  possible  education,  carefully  directed  towards  a 
particular  end,  and  although  all  other  conditions  are  fav- 
ourable, many  persons  completely  fail  of  attainment.  They 
fail  because  they  lack  inherited  aptitudes. 

It  is  true  that  defective  capacities  may  be  improved  by 
careful  training,  but  only  to  a  very  moderate  degree. 
Sooner  or  later  we  reach  a  limit  which  cannot  be  sur- 
passed. 

Inherited  tendencies  are  thus  invariably  the  primary 
determinants  for  the  manifestation  of  mental  capacities. 

Inheritance  in  the  narrowest  sense  does  not  necessarily 
obtain  as  regards  this  development  of  mental  capacities, 
inasmuch  as  parents  and  children  differ  in  many  respects. 
Parents  with  very  moderate  endowments  may  have  chil- 
dren whose  talents  are  altogether  exceptional,  whilst  highly 
gifted  parents  may  have  offspring  of  mediocre  capacity. 
But  the  explanations  previously  given  show  that  these  oc- 
currences are  by  no  means  inconsistent  with  the  general 
doctrine  of  heredity.  The  great  gift  possessed  by  one 
parent  may  be  counteracted  in  consequence  of  the  slight 
development  or  the  absence  of  the  like  capacity  in  the 
other  parent ;  conversely  it  is  possible  that  a  summation 
of  moderate  capacities  in  the  parents  may  lead  to  the  ap- 
pearance of  a  remarkable  talent  in  the  child.  We  also  have 
to  take  into  account  the  possibility  that  the  strength  of 
the  faculties  in  the  children  may  be  conditioned  by  the 


Significance  of  diseases  to  Offspring     85 

state  of  these  faculties,  not  only  in  the  parents,  but  also 
in  the  grandparents. 

Inheritance  is  naturally  most  conspicuous  when  we  are 
able  to  note  the  existence  of  similar  peculiarities  in  pro- 
genitors and  children.  Examples  of  such  inheritance  are 
frequently  encountered  in  everyday  life.  Parents  in  any 
way  distinguished  very  often  have  children  with  the  same 
or  similar  gifts.  De  Candolle,  among  others,  has  studied 
the  inheritance  of  certain  characteristics  among  the  elected 
members  of  the  Paris  Academy,  individuals  chosen  from 
all  countries  as  members  of  the  Academy  on  account  of 
their  distinguished  qualities.  He  reports  five  cases  in 
which  father  and  son  were  both  members  of  this  body, 
and  quite  a  number  of  instances  in  which  academicians 
had  a  distinguished  father  or  a  distinguished  son. 

To  obtain  a  more  precise  understanding  of  such  relation- 
ship it  is  necessary  to  draw  up  family  histories,  taking 
differential  note  of  all  those  members  exhibiting  the  dis- 
tinctive qualities  under  consideration.  Such  family  his- 
tories must  be  as  complete  as  possible,  and  must  extend 
to  as  many  generations  as  possible,  dealing  with  the  two 
parents,  the  four  grandparents,  the  eight  great-grandpar- 
ents, the  sixteen  great-great-grandparents,  etc.  It  must 
deal,  that  is  to  say,  with  the  mother's  ancestors  as  well  as 
with  the  father 's.  Such  comprehensive  family  histories  are 
termed  pedigrees,  and  they  comprise  data  relating  to  all 
the  ancestors  as  far  back  as  possible.  Their  establishment 
in  this  connexion  is  a  recent  practise.  Formerly  investi- 
gators were  for  the  most  part  content  with  the  so-called 
genealogical  trees,  starting  from  a  single  ancestor,  and  dis- 
playing all  his  descendants.  If  by  the  aid  of  such  a  gen- 
ealogical tree  we  wish  to  ascertain  the  conditions  as  to  the 
inheritance  of  some  living  member  of  the  family,  we  can 
do  this  but  very  imperfectly,  for  the  tree  will  give  us  the 
father,  grandfather,  great-grandfather,  etc.,  but  contains 
little  or  no  information  as  to  the  ancestors  of  the  mother, 
grandmother,   etc.     Thus  the   genealogical  tree  gives  an 


86  Heredity,  Disease  and  Human  Evolution 

altogether  inadequate  view  of  the  possibility  of  inheritance 
through  the  female  members  of  the  family.  Moreover,  the 
males  of  the  family  whose  names  appear  in  the  genealogi- 
cal tree  are  only  in  part  those  concerned  in  direct  inher- 
itance ;  the  uncles,  nephews,  etc.,  of  the  individual  whose 
heredity  we  are  considering,  are  out  of  the  direct  line, 
and  are  of  interest  only  to  this  extent,  that  they  may 
afford  evidence  of  the  strength  and  kind  of  inheritance  in 
individual  generations.  We  may  find,  for  example,  that 
the  grandfather  is  apparently  healthy  whilst  his  brothers 
and  sisters  are  all  diseased.  In  such  a  case  it  is  probable 
that  the  grandfather  possessed  the  same  characteristic  in  a 
latent  form.  Pedigrees,  therefore,  are  more  complete  and 
valuable  statements,  but  we  may  also  use  genealogical 
trees  to  supplement  our  information. 

Numerous  investigations  have  been  made  with  the  aid 
of  pedigrees  and  genealogical  trees. 

Galton  was  the  first  to  study  the  inheritance  of  excep- 
tional endowments,  or,  as  he  expressed  it,  the  inheritance 
of  genius.  He  examined  the  case  of  several  hundred  men 
who  had  attained  distinction  in  various  professions,  and 
was  able  to  show  that  in  half  or  more  of  his  instances  these 
men  belonged  to  families  in  which  there  had  been  other 
members  of  note,  and  sometimes  quite  a  number  of  such. 
His  average  results  were  that  in  the  case  of  one  hundred 
men  of  genius,  thirty-one  had  distinguished  fathers,  forty- 
one  distinguished  brothers,  forty-eight  sons  of  note,  and  in 
several  cases  three  or  more  such  near  relatives  attained 
distinction.  In  seventeen  cases  grandfathers,  in  eighteen 
uncles,  in  twenty-two  nephews,  in  fourteen  grandsons,  were 
persons  of  conspicuous  ability;  while  quite  a  number  of 
more  distant  relatives  exliibited  marked  talent.  The  con- 
clusion was  that  high  mental  endowment  is  an  inheritable 
family  peculiarity.  It  appeared  also  that  the  inheritance 
of  such  qualities  is  conspicuous  in  proportion  to  the  close- 
ness of  the  relationship. 

The  occurrence  of  specialised  endowments  in  individual 


Significance  of  Diseases  to  Offspring     87 

families  affords  us  an  illuminating  complement  to  the  re- 
sults of  such  general  investigations  as  that  of  Galton.  For 
example,  the  genealogical  tree  of  the  Bach  family  shows 
us  that  its  members  during  five  generations  were  in  many 
cases  distinguished  by  notable  musical  capacity.  In  the 
fourth  generation  comes  Johann  Sebastian  Bach,  of  whose 
eight  children  four  exhibited  exceptional  musical  endow- 
ment. One  of  his  brothers,  not  himself  musical,  had  six 
children,  five  of  whom  displayed  musical  talent. 

Karl  Pearson  gives  us  a  family  tree  comprising  forty- 
eight  members  during  five  generations.  Twenty-one  of 
these  exhibited  exceptional  gifts,  some  in  the  field  of  sci- 
ence, others  in  that  of  politics. 

We  have  hitherto  considered  intellectual  endowments 
mainly.  What  do  we  find  as  far  as  moral  qualities,  pecu- 
liarities of  character,  are  concerned  ?  The  same  conditions 
obtain;  these  qualities  also  are  transmitted  by  inheritance. 
It  is  not  necessary  to  discuss  the  matter  in  detail,  and  it 
will  suffice  to  point  out  that  already  in  childhood  differ- 
ences in  hereditary  moral  equipment  are  easy  to  recog- 
nise. How  deeply  rooted  in  the  human  mind  is  the  con- 
viction of  the  heritability  of  moral  qualities  is  evident  in 
the  ecclesiastical  view  that  all  men  are  sinful  because  of 
the  sin  of  the  first  human  pair,  and  that,  as  a  punishment 
for  this  primal  transgression,  the  taint  of  original  sin  has 
been  transmitted  to  all  descendants. 

We  may  sum  up  the  discussion  by  saying  that  man  with 
all  his  qualities  is  a  product  of  his  ancestry,  that  he  has 
inherited  from  these  the  rudiments  of  all  his  character- 
istics. 

Many  persons,  and  especially  parents,  are  apt  to  exhibit 
a  certain  uneasiness  in  face  of  this  conclusion.  I  have 
often  heard  it  said  that  if  this  were  true  we  should  be 
forced  to  doubt  the  possibility  of  educating  children  at 
all.  If  all  capacities,  all  characteristics,  all  moral  quali- 
ties, are  determined  by  inheritance,  how  can  we  hope  to 
effect  the  desired  results  by  the  instruction  and  upbringing 


88  Heredity,  Disease  and  Human  Evolution 

of  children?  In  answer  to  such  a  line  of  argument  we 
must  first  of  all  point  out  that  the  human  being  simply 
as  such,  by  the  human  nature  he  shares  with  others,  is 
restricted  in  respect  of  the  possibilities  of  his  development. 
No  mental  capacity  is  capable  of  indefinite,  of  boundless 
increase.  This  fact  is  indisputable.  When,  moreover,  we 
direct  our  attention  to  individual  characteristics,  no  one 
finds  that  there  is  anything  contradictory  when  it  is 
pointed  out  that  the  development  and  the  developmental 
capacity  of  all  these  characteristics  vary  extraordinarily 
from  individual  to  individual.  Every  one  knows  that  per- 
sons constitutionally  stupid  cannot  become  clever;  that 
one  without  musical  talent  cannot  become  musical ;  that 
one  whose  moral  equipment  is  primarily  bad  cannot  be 
made  perfectly  moral.  Thus  we  see  that  the  unwillingness 
to  admit  the  significance  of  heredity  is  motived  mainly  by 
personal  interests.  The  parents  who  revolt  against  the 
foregoing  conclusion  desire  above  all  that  their  children 
should  possess  the  fullest  possibilities  of  development, 
should  not  be  fettered  by  inheritance.  To  such,  as  to  all 
who  have  to  do  with  the  upbringing  of  children,  we  reply 
that  inherited  aptitudes  are  not  of  course  to  be  regarded 
as  rigid  and  unalterable  characteristics.  Sufficient  stress 
has,  on  the  contrary,  been  laid  upon  the  fact  that  all 
aptitudes  are  susceptible  of  development.  It  is  here  that 
education  steps  in  and  finds  a  wide  field  for  its  influence. 
For  the  most  part  education  means  nothing  more  than 
the  fullest  possible  cultivation  of  those  pre-existing  apti- 
tudes which  are  good,  and  which  will  be  found  valuable 
in  the  subsequent  course  of  life,  and  the  repression  of  those 
qualities  that  are  comparatively  valueless  or  positively  evil. 
By  cultivation,  the  advantageous  characteristics  may  often 
be  perfected  to  an  astonishing  degree.  Bad  qualities,  on 
the  other  hand,  may  be  repressed,  in  part  by  instruction, 
and  in  part  by  the  avoidance  of  opportunities  for  their 
exercise.  Manifold  experiences  teach  us  that  any  faculty 
which  is  permanently  put  out  of  use  undergoes  gradual 


Significance  of  Diseases  to  Offspring     89 

atrophy.  Education  can  obtain  fruitful  results  on  the 
basis  of  these  possibilities.  We  must,  indeed,  be  careful  to 
avoid  pitching  our  expectations  too  high.  No  amount  of 
cultivation  will  improve  any  particular  faculty  beyond  a 
certain  limit  which  is  imposed  by  hereditary  possibilities. 
Certain  evil  tendencies  we  shall  find  it  possible  to  repress 
in  some  degree,  but  never  to  eradicate  completely.  How- 
ever much  we  may  war  against  them,  they  will  force 
themselves  to  the  front  when  opportunity  is  given.  It 
follows  then  that  the  matter  of  supreme  importance  is 
to  avoid  the  occurrence  of  such  opportunities. 

Human  beings  will  always  remain  different.  There  will 
always  be  individuals  who  are  exceptionally  capable,  now 
in  one  direction,  now  in  another.  It  is  an  especially  im- 
portant task  of  education  to  cultivate  in  children,  and  if 
necessary  to  discover,  those  features  by  which  they  are 
distinguished  from  others,  in  order  to  bring  these  to  their 
highest  possible  development,  even  if  this  special  cultiva- 
tion does  not  correspond  to  the  wishes  of  the  parent  and 
the  teacher.  Recently  Ostwald,  in  his  extraordinarily  valu- 
able book  Grosse  Manner  has  advocated  this  view.  He  lays 
great  stress  on  the  fact  that  precocious  individuals  need 
peculiar  care,  because  such  individuals  conceal  within  them 
the  potentiality  of  genius.  We  need  men  of  genius,  or  to 
express  the  matter  in  more  general  terms,  we  need  great 
men,  men  who  will  show  us  the  way.  We  shall  obtain 
them,  not  by  a  levelling  education,  not  by  a  system  which 
will  produce  as  few  contrasts  as  possible,  but  by  one  which 
cultivates  marked  aptitudes.  We  must  create  individuali- 
ties which  in  one  sphere  or  another  will  furnish  us  with 
high  results  or  even  the  highest  attainable  to  man.  But 
every  comparatively  slight  aptitude  must  also  receive  due 
attention.  One  only  whose  capacities  have  been  developed 
to  the  fullest  possible  extent  will  be  able  to  lead  a  satis- 
factory life.  This  matter  will  be  more  fully  discussed  in 
the  concluding  chapter. 

We  have  now  to  consider  the  significance  of  human  her- 


90  Heredity,  Disease  and  Human  Evolution 

edity  from  another  aspect,  I  mean,  as  far  as  the  behaviour 
of  the  different  races  of  man  is  concerned,  and  that  of 
the  different  varieties  within  the  great  racial  subdivisions. 
It  cannot  be  doubted  that  at  the  present  time,  at  any  rate, 
the  differences  between  the  white,  yellow,  and  black  races 
are  no  longer  referable  to  the  external  conditions  of  life. 
Every  race  is  to-day  distinguished  from  the  others  by  a 
number  of  altogether  inalterable  characteristics,  character- 
istics which  have  been  inherited  for  innumerable  genera- 
tions and  will  be  inherited  for  innumerable  generations  to 
come.  If  a  race  be  transplanted  into  the  vital  conditions  of 
another  race,  its  characteristics  remain  unaffected.  This 
is  obvious  in  the  case  of  the  American  negroes,  who  have 
remained  unchanged  in  their  new  home.  The  possibility 
is  not  therefore  excluded  of  the  lower  races  ever  suc- 
ceeding in  attaining  to  the  level  of  the  higher.  Distinc- 
tions that  are  the  expression  of  unmistakable  differences  in 
brain  structure  will  persist,  because  such  peculiarities  in 
each  race  will  always  be  transmitted  by  inheritance.  It 
will,  certainly,  remain  possible  for  isolated  individuals  of  a 
lower  race  to  be  capable  of  assimilating  the  acquirements 
of  a  higher  civilisation,  for  among  the  members  of  the 
lower  races,  just  as  much  as  among  those  of  the  upper, 
hereditary  capacities  are  variously  distributed.  The  aver- 
age level  of  development,  however,  remains  below  that  of  the 
higher  races. 

Nor  can  the  marriage  of  whites  with  blacks  effect  any 
change  here.  The  half-breeds,  it  is  true,  are  better  organ- 
ised than  the  blacks,  but  worse  organised  than  the  whites. 
If,  therefore,  mixed  marriages  were  to  become  the  rule, 
the  average  level  of  humanity  would  sink  below  that  of 
the  whites.  The  net  result,  therefore,  under  all  conditions, 
would  be  deterioration ;  and  for  this  reason  we  must  always 
advise  against  marriages  between  blacks  and  whites. 

This  permanence  of  characteristics  does  not  merely  apply 
to  the  great  racial  divisions,  but  extends  also  to  all  the 
varieties  within  those  divisions.     In  the  latter  case  we 


Significance  of  Diseases  to  Offspring     91 

have  no  longer  or  very  little  to  do  with  higher  or  lower 
human  groups,  but  either  with  groups  which,  though  dif- 
fering in  physical  qualities,  are  nevertheless  biologically 
of  equivalent  values,  or  with  groups  whose  individual  men- 
tal qualities  may  indeed  differ  to  some  extent,  but  which 
are  in  essentials  so  similar  as  to  appear,  on  the  whole, 
competent  for  the  discharge  of  the  same  functional  activi- 
ties. 

We  see,  for  example,  that  the  individual  peoples  of 
Europe  differ  from  one  another  in  many  respects.  We  are 
convinced  that  these  differences  are  not  dependent,  or  are 
not  mainly  dependent,  upon  the  varying  vital  conditions 
of  the  respective  countries,  but  that  we  have  to  do  with 
characteristics  which  have  been  transmitted  by  inheritance 
for  hundreds  and  thousands  of  years.  The  Jews  afford  a 
striking  instance  of  such  a  process.  Under  the  most 
diverse  vital  conditions,  living  among  the  most  different 
peoples  and  in  the  most  widely  separated  parts  of  the 
earth,  they  have  preserved  numerous  characteristics  un- 
changed for  two  thousand  years. 

What  is  true  of  the  nations  as  a  whole  is  true  also  of 
particular  groups  within  these  nations,  for  between  these 
also  differences  are  often  plainly  manifest.  Thus  it  is 
easy  to  distinguish  a  Frenchman  of  the  south  from  one 
of  the  north,  an  Irishman  from  an  Englishman,  a  Ger- 
man of  the  Rhenish  provinces  from  one  of  Westphalia,  a 
Prussian  in  the  eastern  part  of  the  kingdom  from  a  native 
of  German  Poland,  and  so  on.  The  distinction  between 
them  is  based  upon  the  differences  between  the  hereditary 
characteristics  which  are  regularly  transmitted  from  gen- 
eration to  generation. 

It  is  true  that  all  these  sub-varieties  of  humanity  within 
the  different  countries  are  less  sharply  distinguished  one 
from  another  than  are  the  major  sub-divisions  of  the 
human  race,  and  this  especially  for  the  reason  that  within 
the  limits  of  a  single  nation  intermarriage  is  so  freely 
effected,  leading  to  a  mingling  of  the  distinctive  charac- 


92  Heredity,  Disease  and  Human  Evolution 

ters.  Moreover,  such  marriages  are  not  open  to  the  same 
objections  as  are  those  between  blacks  and  whites.  They 
may,  on  the  contrary,  have  a  favourable  influence,  because 
advantageous  characteristics  which  are  separate  in  the  two 
varieties  may  be  united  in  the  offspring  of  the  mixed  mar- 
riages. 

With  regard  to  this  question  of  mixed  marriages,  it  is 
of  remarkable  interest  that  these  do  not  always  lead  to  an 
inseparable  mingling  of  the  distinctive  qualities  of  the 
parents,  rendering  it  impossible  to  detect  these  qualities 
separately  in  the  offspring.  This  may,  indeed,  occasionally 
happen.  For  example,  mulattoes,  with  a  few  exceptions 
subsequently  to  be  considered,  have  a  tint  of  skin  inter- 
mediate between  that  of  negroes  and  whites.  Commonly, 
however,  when  human  varieties  intermarry,  the  individual 
characteristics  appear  distinctively  in  subsequent  genera- 
tions, as  in  the  case  of  blond  and  black  hair.  This  separa- 
tion of  qualities  will  receive  detailed  consideration  pres- 
ently. 

For  the  present,  in  this  connexion,  we  shall  only  refer 
to  the  fact  that,  in  view  of  such  experiences,  an  attempt 
has  been  made  to  demonstrate  in  the  members  of  a  nation 
or  in  a  sub-variety  of  that  nation  the  part  played  in  earlier 
times  by  the  peoples  of  other  nations.  If  in  the  members 
of  any  nation  we  find  physical  peculiarities  which  do 
not  appear  to  harmonise  properly  with  its  accepted  his- 
torical origin,  but  which  are  regularly  present  in  the 
inhabitants  of  some  other  country,  we  may  infer  that  the 
latter  at  one  time  came  into  contact  with  the  former,  and 
took  part  in  its  genesis  by  way  of  marriage.  For  instance, 
especial  attention  has  been  directed  to  the  manner  in  which 
the  Germans  have  left  traces  among  many  peoples,  having 
permeated  these  in  popular  migrations  and  in  wars,  and 
having  to  some  extent  settled  among  them.  In  northern 
Italy  we  not  infrequently  encounter  persons  of  Germanic 
type  (with  blond  hair,  blue  eyes,  etc.),  and  by  some  the 


"    Significance  of  Diseases  to  Offspring     93 

significance  of  this  German  admixture  among  the  inhabit- 
ants of  Italy  has  been  esteemed  of  very  great  importance. 
Some  believe  that  a  large  number  of  the  leading  men  of 
the  Renaissance  may  be  regarded  as  of  German  origin.  It 
has  been  supposed  that  a  similar  influence  can  be  traced 
in  France  and  Spain,  the  indications  of  the  admixture  of 
German  blood  being  fairness  of  skin  and  hair,  blue  eyes, 
great  stature,  etc.  It  is  unquestionable  that  enthusiasts 
in  this  direction  have  often  pushed  their  conclusions  be- 
yond the  measure  of  reason,  but  in  principle  the  method  of 
investigation  is  a  sound  one. 

Such  deductions  have  been  carried  even  further,  and 
the  attempt  has  been  made  with  their  assistance  to  analyse 
racial  admixture  within  the  limits  of  any  nation,  and  in 
particular  as  far  as  the  Germans  are  concerned.  One  race, 
the  Germanic,  is  said  to  be  characterised  by  the  features 
just  enumerated ;  another,  the  Alpine  race,  being  distin- 
guished by  a  round  head,  dark  hair  and  eyes,  and  small 
stature.  From  the  mingling  of  these,  the  population  of 
south  Germany  is  supposed  to  have  originated,  and  in  this 
population  the  characteristics  of  the  two  primary  races 
can  still  be  traced.  It  is  possible  to  distinguish  indi- 
viduals who  appear  to  belong  w^holly  or  mainly  to  one 
race  or  to  the  other.  Speaking  generally  it  is  contended 
that  the  fair  race  is  the  more  capable.  The  upper  classes 
of  the  population  belong  predominantly  to  this  race,  the 
lower  classes  predominantly  to  the  other.  Among  the 
lower  classes,  dolichocephalic  or  long-headed  individuals 
again  and  again  emerge,  and  work  their  way  into  the 
upper  strata ;  they  migrate  also  from  the  country  districts, 
populated  chiefly  by  the  lower  section  of  the  race,  into 
the  towns,  where  the  higher  section  has  settled.  We  will 
not  pursue  these  speculations  further.  The  matter  came 
under  consideration  merely  in  order  k)  make  it  clear  how 
far  many  people  are  willing  to  go  in  their  appreciation 
of  the  phenomena  of  heredity. 


94  Heredity,  Disease  and  Human  Evolution 

2.    Principles  of  Inheritance 

In  order  to  gain  a  clear  understanding  of  heredity  it 
is  necessary  to  grasp  the  normal  relationships  of  the  proc- 
ess of  reproduction,  and  a  short  sketch  of  this  latter  must 
therefore  be  given. 

We  may  regard  it  as  a  matter  of  general  knowledge  that 
all  multicellular  organisms  (metazoa),  in  contradistinction 
to  the  unicellular  organisms  (protozoa),  are  produced  by 
germinal  cells,  proceeding  from  egg-cells  or  ova  after  these 
have  been  fertilised  by  sperm-cells  or  spermatozoa.  These 
cells,  microscopic  in  size,  are  generated  in  the  interior  of 
the  parental  body,  in  the  reproductive  glands.  The  female 
reproductive  element,  the  ovum,  continues  after  fertilisa- 
tion and  until  the  birth  of  the  new  individual  to  develop 
within  the  maternal  organism,  and  within  the  embryo  dur- 
ing this  period  new  reproductive  cells  come  into  being. 

The  development  of  the  child  from  the  fertilised  ovum 
will  be  elucidated  by  a  simplified  statement.  In  order  to 
make  it  comprehensible  to  the  general  reader,  numerous 
details  of  great  interest  and  indispensable  to  a  strictly  sci- 
entific study  of  the  subject  must  necessarily  be  omitted 
from  consideration. 

The  ovum,  consisting,  like  all  other  cells,  of  a  cell-body 
and  of  a  nucleus  (the  latter  being  composed  of  material 
similar  to  that  of  the  cell-body  but  different  in  certain 
respects),  is  not  susceptible  of  further  development  until 
after  fertilisation,  that  is  to  say,  after  its  union  with  the 
spermatozoon. 

The  characteristic  feature  of  fertilisation  is  the  penetra- 
tion of  the  ovum  by  the  spermatozoon.  The  two  cells  unite 
to  form  a  single  cell,  and,  above  all,  the  two  cell-nuclei 
coalesce  to  form  a  single  nucleus.  As  a  result  of  the  fusion 
of  these  two  cells,  there  comes  into  existence  the  single 
cell  which  is  known  as  the  fertilised  ovum. 

It  is  essential  to  recognise  that  the  germinal  cells  con- 
tain within  themselves,  in  a  manner  subsequently  to  be 


Significance  of  Diseases  to  Offspring     95 

explained,  all  the  characteristics  distinctive  of  the  parental 
organism.  Only  in  this  way  is  it  possible  that  the  off- 
spring that  are  produced  from  the  germinal  cells  shall  re- 
semble the  parents.  It  is  obvious,  however,  that  in  the 
tiny  germinal  cells  these  characteristics  must  exist  in  some 
potential  form,  and  that  the  fully  developed  peculiarities 
of  the  adult  can  only  grow  gradually  out  of  these  poten- 
tialities. When  the  two  germinal  cells  fuse  to  form  the 
fertilised  ovum,  the  potential  characteristics  likewise  min- 
gle, presumably  in  such  a  way  that  the  similar  character- 
istics coalesce.  The  result  is  that  the  fertilised  ovum  must 
contain  the  qualities  of  both  parents.  It  is  commonly  as- 
sumed, and  the  view  will  here  be  accepted,  that  the  cell- 
nuclei  are  the  real  transmitters  of  parental  characteristics, 
that  they  are  in  fact  the  immediate  agents  in  the  process 
of  inheritance. 

The  ovum  now  begins  to  divide  (cf.  Pig.  3).  As  in  all 
cases  of  cell-division,  the  nucleus  divides  first,  by  a  compli- 
cated process  which  cannot  here  be  described.  The  two 
halves  of  the  divided  nucleus  move  apart,  and  as  this 
movement  takes  place  a  constriction  forms  round  the  cell 
between  them.  This  process  of  division  has  been  spoken  of 
as  furrowing,  because  a  furrow  forms  running  right  round 
the  cell,  and  deepens  until  complete  separation  is  effected. 
There  are  now  two  cells,  two  segmentation-spheres.  De- 
velopment proceeds  by  the  further  subdivision  of  each  of 
these,  to  produce  four  cells  in  all.  The  process  is  repeated 
again  and  again,  giving  rise  by  successive  subdivisions  to 
8,  16,  32,  6-i  cells,  and  so  on.  Thus  an  agglomeration  of 
cells  is  gradually  formed,  and  bj'^  the  subsequent  complex 
transformations  of  this  and  by  a  continued  process  of  cell- 
division  the  individual  parts  of  the  body  and  the  various 
organs  are  formed.  "We  shall  not  here  follow  these  later 
stages  of  development,  but  shall  consider  the  mass  of  cells 
formed  by  the  first  stages  of  division. 

In  the  earliest  phases  of  development  there  is  thus  pro- 
duced a  hollow  sphere,  the  wall  of  which  is  composed  of 


96  Heredity,  Disease  and  Human  Evolution 

numerous  conti^ous  cells  arranged  in  layers  (Fig.  1). 
This  hollow  cell-sphere  represents  in  our  diagram  the  early 
stage  of  the  embryonic  organism,  out  of  which  the  child 
will  be  gradually  formed  by  a  complex  process  of  transfor- 
mation. He  may  assume,  in  correspondence  with  what 
actually  occurs,  that  upon  the  inner  surface  of  the  sphere, 
that  is  to  say  within  the  body  cavity  of  the  developing 
child,  new  ova  (or  spermatozoa)  make  their  appearance  in 
a  manner  subsequently  to  be  described,  at  the  spot  marked  E. 


Fig.  1. — Explanation  in  Text. 

First,  however,  let  us  reconsider  the  first  processes  of 
division,  and  the  two  or  more  segmentation-spheres  formed 
thereby.  By  the  study  of  these  we  can  learn  the  following 
fact,  which  is  of  the  utmost  importance.  If  we  separate 
the  two  first  segmentation-spheres  each  from  the  other,  a 
thing  we  are  actually  able  to  do  only  in  the  case  of  some 
of  the  lower  vertebrates,  such  as  the  frog,  and  in  inverte- 
brate animals,  and  then  observe  how  the  separated  cells 
behave,  we  find  that  each  of  these  proceeds  to  divide  as  if 
it  were  itself  a  fertilised  ovum,  to  form  two,  four,  eight, 
etc.,  daughter-cells,  so  that  each  primary  segmentation- 
sphere  ultimately  gives  rise  to  the  production  of  a  new 


Significance  of  Diseases  to  Offspring     97 

individual.  It  results  that  the  artificial  separation  of  the 
two  segmentation-spheres  leads  each  to  develop  into  a  new 
living  being,  so  that  we  now  have  two  separate  living  beings 
where,  had  we  not  interfered,  one  only  would  have  come 
into  existence.  This  means  that  each  of  the  two  detached 
segmentation-spheres  has  become  competent  to  effect  that 
which,  under  normal  conditions,  could  be  effected  only  by 
the  two  cells  in  union. 

No  less  interesting  is  it  that  the  four  secondary  seg- 
mentation-spheres are  also  competent  to  take  on  the  same 
function,  though  they  do  this  less  readily  than  the 
two  primary  segmentation-spheres.  It  is  true  that  such 
independent  development  of  the  separated  segmentation- 
spheres  is  far  from  being  the  rule,  and  that  in  many  cases, 
indeed,  they  give  rise  to  the  production  of  only  halves  of 
individuals.  But  this  is  of  comparatively  small  impor- 
tance. For  the  purposes  of  the  present  argument  it  suf- 
fices to  know  that  the  complete  development  of  the  sepa- 
rated segmentation-spheres  is  possible. 

The  more  advanced  the  process  of  cell-subdivision,  the 
more  remote  becomes  the  possibility  that  the  individual 
cells,  if  separated,  will  be  competent  to  undergo  an  inde- 
pendent development ;  and  the  cells  of  the  cell-sphere  shown 
in  the  figure  are  not  individually  competent,  any  more 
than  are  those  of  the  fully  formed  individual  into  which 
that  cell-sphere  will  subsequently  develop,  to  go  on  grow- 
ing independently  and  to  produce  an  entire  living  being. 
The  cells,  at  this  stage,  have  undergone  differentiation, 
that  is  to  say  each  cell  has  developed  the  peculiar  qualities 
which  belong  to  the  various  cells  of  the  complete  organism. 
Some  of  them  have  become  skin  cells,  others  brain  cells, 
liver  cells,  bone  cells,  etc.  The  diagrammatic  Fig.  2  is  in- 
tended to  represent  this.  The  general  arrangement  cor- 
responds with  that  seen  in  Fig.  1,  for  the  same  hollow 
cell-sphere  is  shown.  But  now  the  cells  bear  different 
insignia,  some  being  marked  with  a  cross,  others  with  a 
ring,  etc.    Each  of  these  insignia  is  intended  to  indicate  a 


9^'  Heredity,  Disease  and  Human  Evolution 

particular  kind  of  cell,  those  marked  with  a  cross  the  skin 
cells,  for  instance,  and  so  on. 

These  different  kinds  of  cells  are  no  longer  competent, 
as  were  the  first  segmentation-spheres,  to  give  rise  by  sub- 
division to  all  the  other  kinds  of  cells.  In  each  kind  of 
cell  the  special  characteristics  peculiar  to  that  kind  have 
come  to  predominate.  ~  The  other  characteristics  are  per- 
haps not  completely  wanting,  but  they  have  receded  so 
far  into  the  background,  have  been  so  greatly  weakened, 


Fig.  2. — Explanation  in  Text. 

that  they  are  no  longer  effectively  functional.  We  are 
led  to  take  this  view  from  experiments  made  with  plants. 
Under  favourable  conditions  portions  of  the  green  leaves 
of  the  begonia,  containing  only  the  cells  characteristic  of 
the  leaves,  may  grow  into  a  complete  plant.  This  shows 
us  that  all  the  other  characteristics  of  the  plant,  including 
the  capacity  to  form  flowers,  etc.,  are  present  in  the  green 
leaves,  but  that  in  ordinary  conditions  they  do  not  mani- 
fest themselves,  they  are  latent.  We  are  justified  in  as- 
suming that  in  the  lower  animals  and  in  man  the  condi- 
tions are  essentially  similar,  but  that  we  are  no  longer  able 
to  evoke  similar  processes  of  growth  from  the  differen- 


Significance  of  Diseases  to  Offspring     99 

tiated  animal  cells.  When  these  cells  divide,  they  repro- 
duce only  their  outi  kind,  and  never  an  entire  organism. 
The  ovum  alone  (and  the  first  segmentation-spheres)  are 
competent  to  develop  into  a  complete  individual.  By  this 
very  fact  the  ovum  is  characteristically  distinguished  from 
all  other  cells.  It  is  not  a  differentiated  cell.  It  still 
contains,  side  by  side  and  equivalent,  all  the  characteris- 
tics which  in  the  organism  subsequently  to  be  formed  will 
be  separately  distributed  among  the  various  parts,  and 
which  undergo  this  separation  during  the  development  of 
the  embryo.  A  further  reference  to  Fig.  2  will  render  this 
clearer.  In  the  hollow  cell-sphere  we  observe  an  especially 
large  cell,  which  Ave  are  to  regard  as  an  ovum.  In  this  cell 
we  see  the  same  little  insignia,  lying  side  by  side,  which 
are  separately  inscribed  on  the  other  cells  of  the  cell-sphere. 
This  signifies  that  the  qualities  of  the  skin  cells,  the  brain 
cells,  the  bone  cells,  etc.,  are  united  in  the  ovum;  that  is 
to  say,  that  the  same  characteristics  are  simultaneously 
present  in  the  ovum  which  in  the  developing  individual 
(the  hollow  cell-sphere)  have  already  become  differentiated. 

This  composition  of  the  ovum  out  of  the  individual  quali- 
ties signifies  that  this  cell,  inasmuch  as  it  is  not  differen- 
tiated, does  not  yet  possess  any  distinctive  function,  has 
at  present  no  specific  part  to  play  in  the  life  of  the  shel- 
tering organism.  The  ovum  rests  quietly  in  the  organism, 
divides  there,  forming  new  egg-cells,  but  plays  no  part 
in  the  ordinary  bodily  functions.  Indifferent  to  these 
functions,  it  awaits  fertilisation  and  development  to  form 
a  new  living  being. 

Since,  however,  from  this  ovum  there  may  ultimately 
arise  a  new  individual,  with  all  its  peculiarities,  the  cell 
must  necessarily  contain  within  its  substance,  although 
in  a  manner  whose  nature  remains  unknown  to  us,  all  the 
rudiments  of  this  enormous  multiplicity.  This  is  diagram- 
matically  displayed  in  Fig.  2.  All  the  characteristics  pres- 
ent in  the  cells  of  the  body  are  also  present  in  the  ovum. 
How  is  this  possible?     How  do  these  characteristics  get 


100  Heredity,  Disease  and  Human  Evolution 

into  this  cell?  Our  notions  concerning  heredity  depend 
upon  the  answer  to  this  question. 

Let  us  first  of  all  recall  that  in  the  developing'  individual, 
in  the  hollow  cell-sphere  diagrammatically  represented  in 
Figs,  1  and  2,  there  very  soon  come  into  existence  new  ova 
(E  in  the  figure)  ;  these  undergo  multiplication  as  the 
embryo  grows,  and  in  the  body  of  the  fully  formed  child 
are  found  within  a  special  organ,  the  ovary.  How  can 
these  ova  harbour  within  themselves  such  manifold  pecu- 
liarities? The  same  question  naturally  applies  to  the  case 
of  the  spermatozoa,  but  for  the  sake  of  simplicity  we  con- 
fine our  consideration  to  the  ova. 

The  answer  to  this  question  depends  upon  the  manner 
in  which  the  germinal  cells  are  formed.  In  general  terms 
it  may  be  said  that  there  are  two  different  conceptions  of 
this  process,  which  we  must  describe  in  broad  lines,  ig- 
noring details. 

The  first  possibility  may  be  expressed  by  saying  that 
all  the  cells  proceeding  from  the  fertilised  ovum  and 
forming  the  developing  individual  (the  hollow  cell-sphere 
shown  in  Pig.  2)  are  differentiated  in  one  direction  or 
another.  When  in  the  embryo  new  germinal  cells  now 
arise  this  is  possible  only  in  virtue  of  the  fact  that  a  cer- 
tain number  of  the  cells  lying  in  the  wall  of  the  hollow 
sphere  lose  once  more  all  differentiation.  Thus  only  could 
originate  undifferentiated  cells  such  as  are  the  ova.  In 
this  view  there  first  takes  place  a  differentiation  of  all 
the  cells,  and  there  subsequently  occurs  a  loss  of  differen- 
tiation of  some — a  roundabout  way  which,  it  must  be  ad- 
mitted, seems  rather  improbable. 

Nor  would  this  be  all.  The  mere  fact  that  the  cells 
which  had  to  a  certain  extent  become  differentiated  now 
lost  their  differential  characteristics,  would  not  suffice 
to  furnish  them  with  all  the  qualities  which  they  must 
necessarily  contain  in  order  to  give  them  the  power  of 
forming  a  new  individual.  For  we  have  to  remember  that 
the  loss  of  differentiation  would  give  us  cells  simply  devoid 


Significance  of  Diseases"  to  Ofi'spri'ng  101 

of  differential  characteristics.  Yet  the  germinal  cells  do 
in  fact  contain  all  the  qualities  characteristic  of  the 
parental  body  and  of  the  child  eventually  to  be  developed. 
How  do  they  become  endowed  with  these  characteristics? 

The  answer  given  to  this  question  used  to  be  that  the 
parental  body  must  transfer  to  the  ovum  all  the  char- 
acteristics. The  parental  body  introduced  them  from  itself 
and  within  itself  into  the  ova  or  spermatozoa.  To  refer 
once  more  to  the  diagram  in  Fig.  2,  it  is  supposed  that  all 
the  crosses,  rings,  etc.,  which  represent  the  chara;cteristics 
are  transferred  from  the  body-cells  to  the  ovum,  so  that,  as 
the  figure  shows,  they  all  become  united  in  that  cell.  If 
this  really  took  place  the  germinal  cells  would  ultimately 
acquire  all  the  peculiarities  which  we  have  to  assume  it 
to  contain,  and  the  resemblance  of  the  offspring  to  the 
parent  would  thus  be  comprehensible. 

If,  however,  this  were  a  true  account  of  the  matter,  we 
should  be  forced,  as  said  above,  to  conceive  the  loss  of 
differentiation  which  characterises  the  formation  of  the  ova, 
as  not  merely  a  loss  of  those  qualities  which  were  distinc- 
tive of  the  particular  cells  that  gave  rise  to  the  ova ;  we 
should  further  be  compelled  to  assume  that  cells  had  come 
into  being  devoid  of  any  distinctive  qualities  at  all.  For 
all  the  characteristics  are  to  be  transferred  to  the  cell 
anew  from  the  parent.  But  this  is  an  inconceivable  hypoth- 
esis. No  cell  exists  which  is  a  cell  without  qualification, 
the  abstract  idea  of  a  cell.  All  animal  and  all  vegetable 
cells  possess  specific  qualities,  for  example,  and  at  least,  the 
qualities  of  the  species.  The  cells  of  any  species  can  live 
only  in  the  body  to  which  they  belong.  The  ova  them- 
selves contain  differential  characteristics,  even  though  these 
are  not  externally  manifest — they  possess  not  a  few,  merely, 
but  all  the  characteristics  of  an  individual.  There  are 
no  cells  altogether  devoid  of  differential  qualities,  and  it  is 
inconceivable  that  in  the  formation  of  the  ova  there  can 
occur  an  absolute  loss  of  differentiation,  that  cells  can  come 
into  existence  which  contain  nothing  at  all. 


102  Heredity,  'Bisease  and  Human  Evolution 

For  an  additional  reason  this  conception  must  be  alto- 
gether excluded.  The  germinal  cells  are  endowed  with 
characteristics,  not  only  of  the  parents,  but  also  of  the 
grandparents  and  of  remoter  ancestors.  This  would  be 
impossible  if  in  the  process  of  their  formation  all  their 
differential  qualities  become  non-existent. 

Finally,  how  are  we  to  represent  to  our  minds  the  proc- 
ess by  which  the  parental  qualities  are  supposed  to  be' 
transferred  to  the  undifferentiated  germinal  cells?  Dar- 
win assumed  that  from  all  parts  of  the  body  minute  par- 
ticles, termed  by  him  "pangenes"  or  ''gemmules,"  were 
continually  being  given  off  into  the  blood,  and  by  the  blood 
were  carried  to  the  germinal  cells.  But  this  was  only  a 
makeshift  hypothesis,  and  it  has  now  been  generally  aban- 
doned. Nor  has  any  better  hypothesis  arisen  to  replace 
it  (see  the  next  section). 

We  see,  then,  that  the  idea  that  in  the  genesis  of  the 
germinal  cells  there  occurs  a  total  loss  of  differential  char- 
acteristics is  altogether  untenable. 

According  to  this  second  assumption,  during  the  de- 
velopment of  the  embryo  from  the  ovum,  while  most  of 
the  cells  undergo  differentiation,  such  differentiation  does 
not  affect  them  all;  a  series  of  cells  is  supposed  to  remain 
beside,  as  it  were,  the  developing  individual,  and  preserv- 
ing all  the  essential  characteristics  of  the  ovum.  The  idea 
is  represented  diagrammatically  in  Fig.  3.  This  shows  us 
the  progress  of  development  from  the  single  ovum  a  to 
the  hollow  cell-sphere  e.  The  ovum  first  divides,  as  shown 
at  b  into  two  cells,  at  c  into  four,  at  d  into  many,  and  at 
e  into  a  very  large  number,  which  form  the  wall  of  the 
hollow  sphere.  One  cell,  however,  distinguished  in  the 
figure  by  vertical  striation,  always  remains  undifferenti- 
ated. First  there  is  the  ovum ;  then  one  of  the  two  primary 
segmentation-spheres;  then  one  of  the  four  secondary  seg- 
mentation-spheres; then  one  cell  in  the  agglomeration  d; 
and  finally  the  new  ovum  figured  in  the  interior  of  the 
hollow  sphere  e.    This  diagram  is  intended  to  exhibit  the 


Significance  of  Diseases  to  Offspring  103 

fact  that  apart  from  the  differentiating  cells  there  always 
remains  one  which  retains  the  characters  of  the  ovum,  and 
which  ultimatel}^  becomes  the  ovum  of  the  developing  indi- 
vidual. Thus  there  is  a  continuous  series  from  the  ovum  of 
the  former  to  the  ovum  of  the  new  living  creature. 

The  existence  of  the  conditions  pictured  in  the  diagram 
is  not  solely  a  matter  of  deduction.     Boveri  has  shown  in 


Fig.  3. — Explanation  in  Text. 


lower  animals  (the  roundworm  of  the  horse)  that,  from 
the  primary  division  of  the  ovum  onwards  through  the 
whole  course  of  development,  it  is  possible  to  follow  the 
growth  of  a  definitely  characterised  cell-series  analo- 
gous to  that  figured,  and  that  it  is  from  the  elements  of 
this  cell-series  that  the  germinal  cells  of  the  new  individual 
subsequently  proceed.  This  cell-series  may  be  called  the 
germinal  series.  In  other  animals  we  find  more  or  less 
definite  indications  of  an  identical  process,  and  even  in 
human  beings  relevant  observations  have  been  made. 


104  Heredity,  Disease  and  Human  Evolution 

The  fact  that  the  germinal  cells  contain  the  character- 
istics of  the  parents,  and  therewith  also  those  of  the  devel- 
oping individual,  no  longer  offers  difficulties.  For  according 
to  this  conception  of  the  germinal  series  there  arise  from 
the  ovum,  not  only  the  new  individual,  all  of  whose  cells 
are  produced  by  cell-subdivision  of  the  ovum,  but  also  the 
new  ova  found  in  the  body  of  this  new  individual,  which 
derive  in  a  direct  line  of  descent  from  the  old  ovum.  The 
new  individual  and  the  new  ova  thus  derive  from  the 
same  source.  For  this  reason  the  new  ova  must  contain  all 
the  qualities  which,  in  the  individual,  are  distributed  among 
the  various  differentiated  cells. 

In  this  way  we  attain  to  an  extraordinarily  simple  ex- 
planation of  heredity.  Parents  and  children  must  neces- 
sarily harmonise  with  one  another  in  the  main  because 
both  parents  and  children  derive  from  the  same  cells,  that 
is  to  say,  from  the  germinal  cells  of  the  grandparents. 

Yet,  for  two  reasons,  parents  and  children  can  never 
be  completely  alike. 

In  the  first  place,  the  germinal  cells  may  undergo  altera- 
tion during  their  sojourn  in  the  parental  body.  Numerous 
influences  may  aft'ect  them,  and  these  will  be  considered 
in  the  next  section.  Above  all  it  is  possible  that  illness 
affecting  the  parents  may  injure  the  germinal  cells. 

The  second  reason  is  one  of  yet  wider  significance.  Abso- 
lute similarity  between  the  offspring  and  the  mother  would 
be  theoretically  conceivable  if  the  offspring  were  derived 
from  the  ovum  alone,  as  happens  in  the  case  of  partheno- 
genesis am.ong  aphides  and  bees.  In  such  cases,  the  off- 
spring must  exhibit  characteristics  precisely  similar  to 
those  of  the  mother.  Parthenogenesis,  however,  does  not 
take  place  among  the  vertebrata.  As  far  as  these  are 
concerned  every  new  individual  originates  out  of  the  union 
of  two  germinal  cells.  In  the  act  of  fertilisation  the  re- 
spective qualities  intermingle  and  must  therefore  manifest 
themselves  in  the  offspring,  although  this  does  not  mean 
that  any  simple  summation  takes  place.    For  the  number 


Significance  of  Diseases  to  Offspring  105 


of  characteristics  in  the  child  is  no  greater  than  the  niim-> 
ber  in  the  parents.  Many  characteristics  are  derived  in 
common  from  both  parents, 
while  other  characteristics 
that  exist  in  one  or  other  or 
both  parents  are  not  manifest 
in  the  offspring.  In  any  case, 
the  children  must  exhibit 
more  or  less  extensive  differ- 
ences when  compared  with 
either  parent. 

Fig.  4  is  a  diagram  to  make 
the  considerations  plainer. 
We  see  first  three  simply 
planned  hollow  cell-spheres, 
A,  B,  C,  and  in  the  interior 
of  these  the  germinal  cells,  a, 
b,  c.  From  the  germinal  cell, 
a,  fertilised  at  a,  by  conjunc- 
tion with  the  male  germinal 
cell  derived  from  the  individ- 
ual Ai,  there  arises,  as  indi- 
cated by  the  line  marked  2, 
the  individual  B  and  its 
germinal  cell  b,  this  latter 
being  also  connected  with  the 
germinal  cell  a  by  means  of 
the  straight  line  1,  1  which 
traverses  the  whole  series  of 
individuals  A,  B,  C.  A  simi- 
lar succession  of  relationships 
obtains  between  B  and  C.  The 
fertilised  germinal  cell  b 
gives  rise  both  to  the  indi- 
vidual C  and  to  its  germinal  cell  c.  Now,  since  th3  germ- 
inal cell  b  possesses  all  its  characteristics  in  common  with 
the  individual  B,  the  individual  C,  which  derives  from  b 


Fig 


Explanation    in 


106  Heredity,  Disease  and  Human  Evolution 

(bj  must  harmonise  with  B  except  in  respect  of  those 
qualities  which  are  derived  through  the  act  of  fertilisation 
from  B^.  B,  in  turn,  must  harmonise  with  A,  and  the  same 
process  may  be  followed  back  indefinitely  into  the  past,  and 
may  be  conceived  as  continuing  indefinitely  into  the  future. 
In  the  diagram,  however,  the  origin  of  the  germinal  cells 
one  from  another  which  is  characteristic  of  the  process  of 
heredity  is  indicated  by  the  straight  line  which  connects 
them  all.  There  is  displayed  a  continuous  series  of  ger- 
minal cells  from  which  the  isolated  individuals  are  pro- 
duced as  lateral  offshoots.  The  permanent  process  of  he- 
redity from  one  generation  to  another  here  finds  character- 
istic expression.  For  this  process,  whose  theoretical  foun- 
dation we  owe  to  Nussbaum  and  Weismann,  and  its  detailed 
elucidation  to  the  last-named,  we  possess  a  special  name. 
With  Weismann  we  speak  of  it  as  the  continuity  of  the 
germ  plasm. 

3.     Occurrence  in  the  Offspring  of  Qualities 

Acquired  hy  the  Parents 

{Inheritance  of  Acquired  Characters) 

As  regards  the  diffusion  of  diseases  by  way  of  inherit- 
ance it  is  of  great  importance  to  know  whether  morbid 
states  acquired  by  the  individual  can  be  transmitted  by 
inheritance  to  the  offspring.  If  this  were  the  rule,  or  if 
it  were  even  a  possibility,  the  danger  of  diseases  getting 
the  upper  hand  would  be  extremely  great.  The  question 
must  therefore  be  discussed,  but  its  adequate  consideration 
will  be  possible  only  from  an  extended  outlook,  as  part  of 
the  general  problem  of  the  inheritance  of  acquired  char- 
acters. 

In  the  previous  section  an  account  was  given  of  the  proc- 
ess, in  essence  very  simple,  by  which  the  individuals  of  the 
new  generation  proceed  from  the  individuals  of  the  old — 
a  process  that  enables  us  to  understand  the  observed  facts 
as  to  the  similarity  between  progenitors  and  offspring.  We 
saw  that  from  the  ovum  of  the  parent  there  proceeds,  not 


Significance  of  Diseases  to  Offspring  107 

only  the  child,  but  also  the  ova  that  are  found  in  the  child 's 
body,  and  that  the  ova  in  the  child  are  in  direct  line  of 
descent  from  the  ova  of  the  parent.  From  this  it  results 
that  the  body  of  the  child  exhibits  peculiarities  resembling 
those  whose  rudiments  exist  in  the  ova  or  spermatozoa  con- 
tained within  its  own  body.  It  follows,  further,  that  when 
from  an  ovum  of  this  child  there  subsequently  develops  a 
grandchild,  this  latter  must  in  its  turn  exhibit  essentially 
the  same  qualities  as  those  exhibited  by  the  child,  now  in 
its  turn  become  a  parent ;  and  that,  in  addition,  the  germi- 
nal cells  of  the  grandchild  will  be  distinguished  by  the 
same  characteristics  as  the  grandchild  itself,  in  consequence 
of  which  the  germinal  cells  are  enabled  to  transmit  these 
cliaracteristics  to  a  great-grandchild,  and  so  on. 

,  We  laid  stress,  however,  upon  the  fact  that  whilst  in  this 
way  there  arises  an  essential  coincidence  of  qualities  in 
the  successive  generations  of  individuals,  no  perfect  con- 
formity of  characters  ever  ensues.  We  showed  that  the 
principal  reason  for  the  differences  observed  is  that  the 
new  individual  proceeds  from  the  union  of  two  different 
germinal  cells,  and  therefore  contains  an  admixture  of 
the  characteristics  of  both. 

An  extremely  interesting  and  important  question  now 
arises.  Are  the  successive  generations  of  germinal  cells 
different  merely  for  the  reason  that  they  have  experienced 
the  above  described  mingling  of  qualities,  or  may  they  un- 
dergo transformations,  in  addition,  on  account  of  the  oper- 
ation of  external  influences?  In  the  first  place  we  have 
to  ask  in  what  way  such  influences  are  able  to  operate  upon 
the  germinal  cells.  It  is  obvious — if  we  except  violent 
mechanical  injury  and  the  like — that  it  is  impossible  for 
such  influences  to  be  a  part  of  the  direct  working  of  the 
environment ;  they  can  act  only  through  the  intermedia- 
tion of  the  parental  body,  and  by  inducing  changes  therein. 

At  this  point  we  must  clearly  distinguish  between  two 
possibilities.  Such  influences  as  we  are  considering,  if  dif- 
fused throughout  the  parental  body  (as,  for  example,  in 


108  Heredity,  Disease  and  Human  Evolution 

the  form  of  some  chemical  agent),  could  exercise  an  in- 
fluence on  the  parental  body  itself  in  addition  to  any 
changes  they  might  directly  induce  in  the  germinal  cells. 
In  this  case  an  influence  would  simultaneously  affect  the 
parental  organism  and  the  germinal  cells,  but  it  is  clear 
that  we  could  not  speak  of  transmission  from  the  parental 
organism  to  the  germ. 

The  other  possibility,  however,  does  involve  such  trans- 
mission from  the  parents  to  the  germinal  cells.  The  prob- 
lem may  be  stated  as  follows:  Is  it  possible  for  changes 
arising  in  the  parents,  from  any  cause,  to  be  transmitted 
as  such  to  the  germinal  cells,  that  is,  to  affect  these  latter 
without  further  collaboration  on  the  part  of  the  exciting 
causes?  Is  the  transmission  of  acquired  characters  to 
ovum  or  spermatozoon  possible ;  can  inheritance,  in  this 
narrower  sense,  take  place?  The  question  has  been  the 
subject  of  prolonged  controversy,  and  has  received  con- 
flicting answers.  Some  affirm  the  possibility  as  emphati- 
cally as  others  deny. 

On  the  basis  of  what  we  have  learned  in  the  pre- 
vious section  a  theoretical  objection  might  be  raised  to 
the  possibility  of  such  transmission.  We  saw  that  the 
idea  that  the  germinal  cells  derive  their  qualities  through 
the  access  of  extremely  minute  particles  derived  from 
all  parts  of  the  body,  is  one  which  can  no  longer  be  sus- 
tained. The  qualities  of  the  germinal  cells  are  not  de- 
pendent upon  any  such  process,  but  derive  from  the  fact 
that  these  germinal  cells  are  the  direct  offspring  of  those 
of  an  earlier  generation.  This  is  how  it  is  that  heredity 
can  be  so  simply  explained.  The  attempt  might  be  made 
to  deduce  from  these  relationships  that  if  the  characters 
which  the  parents  have  inherited  from  their  parents  are 
without  influence  upon  the  germinal  cells,  for  this  reason 
also  those  characters  which  have  been  induced  in  the  par- 
ents by  the  direct  operation  of  external  noxious  influences 
(over  and  above  the  characters  acquired  by  inheritance) 
must  also  remain  without  influence  upon  ova  and  sperma- 


Significance  of  Diseases  to  Offspring  109 

tozoa.  But  this  conclusion  would  be  unsound,  for  there 
can  be  no  doubt  that  under  certain  conditions  changes  in 
the  parental  body  may  affect  the  germinal  cells.  These 
cells  are  by  no  means  unalterable.  Indeed,  thus  only  is 
the  fact  explicable  that  new  inheritable  diseases  can  come 
into  existence.    Of  this  much  will  have  to  be  said  later. 

It  is,  then,  possible  that  acquired  states  in  the  parents 
may  affect  the  germinal  cells,  and  it  is  often  possible  to 
trace  the  working  of  such  influences.  This,  however,  is  not 
a  complete  answer  to  the  question  under  discussion.  Our 
true  interest  here  is  in  the  other  problem,  whether  these 
new  characters  in  the  parent  affect  the  germinal  cells  in 
such  a  way  as  directly  to  induce  the  formation  of  disposi- 
tions which  will  lead  to  the  appearance  of  the  identical 
characters  in  the  individuals  into  which  the  germinal  cells 
will  subsequently  develop — and  not  in  the  problem  whether 
the  ova  and  spermatozoa  are  affected  in  some  other  way 
than  this.  Such  transmission  of  identical  characters  would 
be  the  inheritance  of  acquired  characters  in  the  strict  sense 
of  the  term. 

Numerous  objections  can  be  urged  against  the  existence 
of  any  such  possibility.  If  it  were  so  easy  for  any  changes 
in  the  parental  body  to  be  transmitted  to  the  germ,  we 
should  be  forced  to  expect  that  all  the  disturbances,  grave 
or  trifling,  continually  induced  by  external  influences  in 
the  individuals  of  successive  generations  would  affect  the 
germinal  cells  and  make  their  influence  felt  upon  the  off- 
spring. Changes  of  all  kinds,  morbid  conditions  of  the 
organs,  injuries,  etc.,  would  necessarily  have  a  cumulative 
effect,  until  ultimately  none  but  abnormal  and  malformed 
individuals  would  ever  be  born.  This  is  not  the  case,  and 
it  necessarily  follows  that  the  transmission  to  the  germi- 
nal cells  of  changes  in  the  parental  organism  is,  at  any 
rate,  not  the  general  rule. 

Is  such  transmission  theoretically  conceivable?  Let  us 
try  to  get  a  clear  understanding  of  what  must  happen  to 
bring  it  to  pass.    It  would  be  necessary  for  any  change  in 


.^•X\  / 


110  Her^^dity,  Disease  and  Human  Evolution 

a  part  of  the  body  to  exercise  an  equivalent  influence  upon 
the  germinal  cell,  inducing  in  the  latter,  in  those  constitu- 
ents out  of  which  the  organ  now  affected  in  the  parent  is 
subsequently  to  develop,  a  change  which,  potentially  speak- 
ing, must  be  precisely  of  the  same  character.  To  give  an 
example,  the  skin  becomes  pigmented,  if  this  colouration  is 
to  be  transmitted  by  inheritance,  it  is  necessary  that  in 
the  rudiment  of  the  offspring  out  of  which  the  skin  will 
ultimately  arise  there  shall  be  induced  a  capacity  for  the 
skin  to  take  on  a  dark  colouration.  How  can  this  occur? 
What  sort  of  relationships  exist  between  parent  and  ger- 
minal cell?  In  the  first  place  there  is  a  spatial  relation- 
ship, inasmuch  as  the  gemiinal  cell  is  encompassed  on  all 
sides  by  the  constituents  of  the  parental  body.  But  the 
parts  of  the  parental  body  contiguous  to  the  germinal  cell 
have  nothing  to  do  with  the  skin  (or  with  any  other  organ) 
and  therefore  we  cannot  admit  the  possibility  that  by  such 
contiguity  the  rudiment  of  the  dark  colouration  can  be 
introduced  into  the  germinal  cells.  This,  however,  is  the 
only  direct  spatial  relationship.  There  are  no  nerves  lead- 
ing from  the  body  of  the  parent  into  the  germinal  cells, 
and  even  if  there  were  such  nerves,  we  could  not  under- 
stand how  changes  in  the  organs  of  the  parent  could  there- 
by be  conducted  to  these  cells.  The  only  demonstrable 
relationship  between  parent  and  offspring  is,  of  primary 
importance,  that  effected  by  the  intermediation  of  the  blood, 
and,  of  secondary  importance,  by  the  other  juices  of  the 
body.  Under  normal  conditions  the  constituents  of  the 
blood  enter  the  ovum,  in  so  far  as  these  constituents  are 
requisite  to  the  nutrition  of  that  cell.  Other  substances, 
artificially  or  unintentionally  introduced  into  the  body, 
may  be  found  in  the  germinal  cells,  and  some  of  these 
are  injurious.  For  example,  the  fat-staining  substance 
known  as  Soudan-red,  when  introduced  into  the  organism, 
is  found  in  the  ova. 

Thus  the  germinal  cells  may  readily  be  influenced  by  / 
chemical  action.     We  have  to  ask,  however,  whether  the/ 

i 
\ 


Significance  of  Diseases  to  Offspring   111 

possibility  of  such  action  can  explain  the  equivalent  trans- 
mission to  the  germ  of  bodily  changes  in  the  parent.  The 
answer  to  this  question  will  become  clear  as  we  proceed. 

But  first  let  us  ask  what  are  the  changes  whose  trans- 
mission to  the  offspring  has  been  supposed  to  occur. 

For  a  long  time,  in  this  connexion,  people  thought  espe- 
cially of  the  hereditary  transmission  of  injuries,  although 
the  non-transmissibility  of  these  is  a  matter  of  every-day 
experience.  No  one  has  ever  seen  a  change  effected  by  a 
surgical  operation  transmitted  to  the  offspring.  Yet  again 
and  again,  in  individual  cases,  this  has  been  supposed  pos- 
sible.   A  few  examples  may  be  given. 

Bechterew  reported  the  case  of  a  bitch  which  in  early 
j^outh  sustained  a  fracture  of  one  of  the  fore-legs ;  this  was 
set  in  a  bad  position,  and  the  offspring  of  the  animal  for 
many  generations  exhibited  a  crookedness  of  one  of  the 
fore-legs.  The  observation,  however,  is  altogether  devoid 
of  precision,  and  the  accidental  deformity  due  to  the  frac- 
ture is  imperfectly  described.  No  proof  is  given  that  the 
bitch  did  not  previously  exhibit  a  congenital  crookedness 
of  this  leg,  the  inheritance  of  which  would  have  been  nat- 
ural enough. 

Another  remarkable  instance  is  reported  by  Lacharias. 
He  describes  tailless  cats,  whose  mother  some  years  before 
had  lost  her  tail  from  injury — having  been  run  over  by  a 
car.  But  there  is  no  precise  record  of  the  injury,  which, 
as  Bonnet  objected,  seems  rather  an  improbable  one.  It 
is  necessary  to  remember  that  there  are  tailless  varieties 
of  eats,  or  rather  cats  with  very  short  stumpy  tails,  and  in 
these  animals  the  absence  of  the  tail  is  of  course  a  hered- 
itary character.  The  cats  in  question  may  have  belonged 
to  one  of  the  tailless  varieties.  In  dogs  also,  as  Bonnet 
has  shown,  a  similar  sturr.py  condition  of  the  tail  is  some- 
times found  as  a  hereditary  character.  In  certain  cases 
in  which  dogs  had  tailless  offspring,  and  it  was  supposed 
that  this  was  due  to  amputation  of  the  tail  in  the  parent 
animals,  he  was  able  to  prove  that  the  cases  were  actually 


112  Heredity,  Disease  and  Human  Evolution 

those  of  the  transmission  of  a  congenital  deformity.  Pre- 
cise inquiry  showed,  moreover,  that  in  the  parent  animal 
amputation  of  the  tail  had  not  been  effected. 

Another  instance  which  at  first  sight  appeared  decisive 
as  to  the  transmission  of  the  effect  of  injury  is  described 
by  Israel.  A  woman  had  an  earring  torn  from  her  ear,  and 
in  her  next  child  there  was  a  cleft  in  the  lobule  of  the 
ear,  apparently  the  hereditary  effect  of  the  laceration  of 
the  mother's  ear.  But  close  examination  of  the  mother's 
ear  showed  that  in  addition  to  the  laceration  resulting 
from  the  injury  there  existed  in  the  lobule  a  congenital 
cleft,  and  that  it  was  this  that  had  been  transmitted  by 
inheritance. 

These  were  mere  casual  observations,  but  certain  experi- 
ments appeared  to  afford  more  weighty  evidence.  Brown- 
Sequard  made  an  extensive  series  of  experiments  on  guinea- 
pigs.  In  these  animals  he  divided  the  sciatic  nerve,  the 
great  nerve  of  the  lower  limb,  and  observed  that  stimula- 
tion of  certain  regions  of  the  same  side  of  the  body  as 
that  on  which  the  nerve  had  been  divided  induced  con- 
vulsive seizures  having  a  general  resemblance  to  those  char- 
acteristic of  epilepsy  in  human  beings.  The  observations 
were  confirmed  by  numerous  investigators.  In  the  animals 
thus  operated  on,  various  other  consequences  ensued,  and 
among  these  were  changes  in  the  paralysed  legs,  leading, 
for  instance,  to  the  loss  of  some  of  the  toes.  Brown- 
Sequard,  and  some  of  those  who  repeated  his  experiments, 
now  observed  that  these  epileptic  seizures  occurred  in  a 
small  proportion  of  the  offspring  of  the  animals  thus 
treated — in  about  two  to  three  per  cent.  He  believed  him- 
self to  have  proved  the  transmissibility  by  inheritance  of 
this  traumatically  induced  epilepsy.  ,  Sommer,  however, 
who  repeated  the  experiments,  and  Maciesza  and  Wrzosek, 
who  undertook  a  more  extensive  series  of  investigations  on 
the  same  lines,  obtained  completely  negative  results.  They 
found  themselves,  therefore,  unable  to  confirm  Brown- 
Sequard's    conclusions.      But  meanwhile    Brown-Sequard 


Significance  of  Diseases  to  Offspring  113 

had  reported  that  the  secondary  changes  in  the  paralysed 
limbs  were  also  occasionally  transmitted  by  inheritance, 
though  in  from  one  to  two  per  cent,  only  of  the  cases.  No 
subsequent  investigator  has  been  able  to  confirm,  this  ob- 
servation. Neither  Dupuis,  a  pupil  of  Brown-Sequard,  nor 
Eomanes,  nor  Sommer,  found  malformations  of  the  feet  in 
the  offspring.  ]\Iaciesza  found  no  such  changes  in  forty- 
four  of  the  offspring  of  guinea-pigs  with  artificially  abnor- 
mal legs.  In  addition,  examining  392  guinea-pigs,  he 
showed  that  malformations  of  the  toes  are  found  also  in 
the  offspring  of  normal  parents  in  about  the  same  propor- 
tions as  in  the  offspring  of  the  animals  operated  on  by 
Brown-Sequard.  To  widen  the  field  of  investigation,  Maci- 
esza  operated  also  on  white  mice,  in  which  animals  sec- 
tion of  the  sciatic  nerve  leads  to  the  onset  of  similar  de- 
formities of  the  toes.  The  offspring  of  454  mice  that 
had  been  operated  on  numbered  1,008,  and  30  of  these,  that 
is  to  say,  about  3  per  cent.,  exhibited  malformations  of 
the  toes.  Examination  of  the  offspring  of  normal  mice 
showed,  however,  that  in  these  the  same  abnormalities  were 
present  in  the  same  proportion  of  instances,  so  that  the 
existence  of  malformation  of  the  toes  in  the  offspring  of 
animals  subjected  to  operation  could  not  be  attributed  to 
inheritance  of  the  results  of  operation. 

These  experiments  demonstrated  the  unsoundness  of  the 
widely  quoted  conclusions  of  Brown-Sequard, 

Weismann  also  obtained  negative  results,  in  a  series  of 
experiments  in  which  he  amputated  the  tails  of  mice  for 
a  number  of  generations.  In  no  instances  were  the  off- 
spring of  these  animals  tailless  or  equipped  with  abnor- 
mally short  tails. 

To-day,  then,  hardly  any  one  ever  alleges  that  the  results 
of  injury  are  transmitted  by  inheritance. 

Diseases  may,  in  this  respect,  be  compared  with  injuries. 
Diseases  may  be  referred  to  bodily  changes  evoked  by 
injurious  environmental  influences,  and  may  therefore,  to 
this  extent,  be  spoken  of  as  injuries.    It  is  true  that  dis- 


114  Heredity,  Disease  and  Human  Evolution 

eases  are  not  usually  induced  by  the  operation  of  mechan-  ' 
ical  instruments,  but  are  dependent  for  the  most  part  upon 
chemical  influences,  and  especially  upon  the  toxins  pro-  I 
duced  by  micro-organisms.     But  many  chemical  disease-  ' 
producing  influences,  such  as  corrosive  acids,  have  effects 
obviously  similar  to  those  of  mechanical  injury.    As  far  as 
these  are  concerned,  the  same  considerations  apply  as  in 
the  case  of  injury.    The  changes  they  induce  are  not  trans- 
mitted to  the  germinal  cells.     Subsequently  this  matter 
will  be  considered  in  further  detail. 

Here  we  shall  refer  merely  to  one  important  considera- 
tion.   The  anatomical  disturbances,  indeed,  cannot  be  trans- 
ferred to  the  germinal  cells,  but  there  may  be  a  specious 
appearance  of  such  a  transference.    When  a  poison  affects 
the  organism  and  is  distributed  through  all  its  parts,  some 
of  it  will  necessarily  reach  the  germinal  cells,  and  it  is 
possible  that  in  these  latter  the  poison  may  influence  the   ■. 
rudiments  of  the  very  organs  which  in  the  parental  body    j 
are   injured   in   their   fully   developed   condition.      There    I 
will  then  ensue  like  changes  in  the  parental  organism  and  j 
in  the  germinal  cells,  and  the  changes  in  the  parental  or-  / 
gans  will  appear  to  have  been  transmitted  to  the  germinal  j 
rudiments.  ^ 

Consider,  for  example,  the  influence  of  alcohol.    In  the 
parent  it  may  affect  the  brain  and  in  the  germinal  cell  the 
brain-rudiment.     In  the  parent  alcohol  may  cause  mental 
disorder,  while  the  germinal  rudiment  may  be  injured  in 
such  a  way  that  the  child  which  subsequently  develops  has 
an  abnormally  constituted  brain,  and  therefore  suffers  from   r 
mental  disease  similar  to  that  which  occurred  in  the  par-  : 
ent.    But  here  obviously  there  is  no  true  process  of  inher-  , 
itance ;  there  is  merely  the  simultaneous  production  of  like  1 
changes  in  two  distinct  regions.  > 

Very  shortly  we  shall  have  to  return  to  this  matter,  and 
it  will  be  referred  to  again  and  again  in  our  subsequent 
discussions. 

Turning  now  from  the  consideration  of  the  inheritance 


Significance  of  Diseases  to  Offspring   115 

of  acquired  injuries  and  diseases  to  that  of  the  inheritance 
of  acquired  characters  or  qualities,  we  must  first  come  to 
an  understanding  as  to  the  precise  signification  of  the  lat- 
ter term. 

We  must  give  the  name  of  characters  or  qualities  to  such 
peculiarities  only  as  attach  to  the  healthy  organism,  and 
to  such  as  harmonise  with  that  organism.  Injuries  and 
diseases  are  not  characters  in  the  narrow  sense  of  the  term. 
Even  if  in  the  widest  signification  of  the  word  we  might 
speak  of  them  as  characters,  we  shall  avoid  doing  so  here 
in  order  that  our  argument  may  be  more  readily  compre- 
hensible. 

The  noinnal  organism  constitutes  a  sum  of  qualities  har- 
moniously combined  and  in  a  state  of  mutual  adaptation. 
Into  this  complex,  completely  new  characters  cannot  be  in- 
troduced. Such  introduction  is  theoretically  inconceivable, 
and  is  impossible  in  practice.  "When  anything  new  is 
acquired  we  always  have  to  do  simply  with  a  changed  adap- 
tation to  foreign  external  conditions,  with  an  intensifica- 
tion, or  the  reverse,  of  existing  characters.  Thus,  the 
hairy  covering  of  the  body  may  become  thicker  in  con- 
sequence of  cold,  or  a  muscle  may  become  more  powerful 
from  exercise.  The  question  now  arises  whether  such  ac-  \^ 
quired  characters  can  be  transmitted  to  the  germ.  \ 

The  answer  to  this  question  presupposes  that  we  have 
answered  another,  and  this  is,  whether  the  germinal  cells 
are  at  all  capable  of  being  transformed  in  a  corresponding 
sense.  On  general  principles  we  cannot  doubt  that  this 
may  occur,  provided  that  the  same  influence  can  operate 
upon  the  germ  as  upon  the  parent.  "When  cold  affects  the  ' 
germinal  cell,  the  skin-rudiment  in  that  cell  will  be  altered 
in  a  sense  identical  with  that  in  which  in  the  parent  the 
developed  skin  is  altered  by  the  same  influence.  Those  who 
accept  the  inheritance  of  acquired  characters  must  them- 
selves admit  the  existence  in  the  germinal  cell  of  such  a 
capacity  for  adaptation,  for  only  on  this  assumption  can 
the  germinal  cell  be  affected  by  the  change  that  takes  place 


116  Heredity,  Disease  and  Human  Evolution 

in  the  parental  body.  If,  however,  the  germinal  cell  pos- 
sesses a  general  capacity  for  adaptation,  it  must  then  be 
competent  to  react  directly  to  the  influence  which  is  simul- 
taneously acting  upon  the  parent. 

Now  let  us  suppose,  for  the  sake  of  argument,  that  ac- 
quired adaptations  can  really  be  transmitted.  How  would 
such  adaptations  make  their  influence  felt  upon  the  ger- 
minal cells?  Certainly  not  by  the  intermediation  of  nerves, 
for  there  are  no  nerves  connecting  the  parental  body  and 
the  germinal  cells.  The  only  remaining  means  of  influence 
is  that  of  substances  in  solution.  But  how  is  it  conceivable 
that  substances  derived  from  the  adapted  parental  parts 
could  in  the  rudiments  in  the  germinal  cells  produce  an 
effect  identical  in  outcome  with  that  which  in  the  parent 
has  been  produced  in  an  entirely  different  way,  and  cer- 
tainly not  by  the  substances  in  solution  that  are  supposed 
to  act  upon  the  rudiments  in  the  germ? 

If,  for  example,  in  the  parental  body,  a  muscle  under- 
goes enlargement  in  consequence  of  prolonged  exercise,  in 
what  way  could  this  increase  in  size  be  transmitted  to  the 
muscle-rudiment  in  the  germinal  cell?  By  means  of  the 
products  of  tissue  change  which  are  increased  in  quantity 
in  consequence  of  the  increased  activity?  But  how  could 
these  products  induce  a  muscular  enlargement  when  the 
muscular  enlargement  in  the  parent  is  itself  the  outcome 
of  repeated  acts  of  contraction  arising  under  the  influence 
of  the  nervous  system,  and  is  in  no  way  conditioned  by 
the  working  of  substances  in  solution  ?  The  strengthening 
of  the  muscle-rudiment  in  the  germinal  cell  could  only 
result  from  the  long  continuance  of  enhanced  demands 
upon  the  activity  of  this  rudiment,  and  there  is  here  no 
question  of  anything  of  the  kind. 

In  accordance  with  these  considerations  we  can  assume 
the  "inheritance"  of  acquired  characters  to  take  place 
in  those  cases  only  in  which  the  same  influence  is  at 
work  upon  the  parental  organ  and  upon  the  corresponding 
nidiment  in  the  germinal  cell.    In  that  case,  however,  we 


Significance  of  Diseases  to  Offspring   117 

are  not  concerned  with  inheritance  in  the  rigid  sense  of 
the  term.  True  inheritance  would  occur  if  the  quality 
were  transferred  as  such  to  the  germ,  but  it  does  not  occur 
when  the  same  conditions  give  rise  to  the  same  result  in 
two  different  places.  Since  such  direct  transference  can- 
not be  demonstrated,  it  follows  that  the  inheritance  of  ac- 
quired characters  in  the  strict  sense  does  not  take  place. 
The  only  question  open  is  whether  we  are  justified  in 
using  the  term  inexactly  to  denote  the  simultaneous  orig- 
ination of  like  changes  in  the  parental  organism  and  in  the 
germinal  cell.  This  abuse  of  terminology  is  very  com- 
mon, but  it  would  be  better  to  avoid  it,  and  always  to 
insist  upon  the  fact  that  what  takes  place  in  these  cases 
is  not  inheritance  but  what  may  be  termed  parallel  induc- 
tion, that  is  to  say,  the  parallel  causation  of  the  change 
in  parent  and  in  germ.  This  explanation  gives  full  satis- 
faction in  all  the  cases  in  which  a  quality  arising  in  the 
parent  appears  also  in  the  offspring,  and  in  which  people 
are  accustomed  (erroneously)  to  speak  of  inheritance  as 
having  taken  place.  It  is  true  that  many  writers  refuse 
to  admit  this,  and  many  experiments  have  been  made  which 
are  supposed  to  establish  the  direct  transmission  of  ac- 
quired characters.  We  must  therefore  briefly  consider 
these  experimental  data  in  order  to  decide  whether  it  is 
really  necessary  to  interpret  them  as  examples  of  true  in- 
heritance. 

Let  us  first  consider  the  well  known  experiments  of 
Standfuss  and  Fischer.  These  investigators  reared  cater- 
pillars and  pupae  of  butterflies  at  a  lower  and  at  a  higher 
temperature  than  customary,  and  observed  that  the  but- 
terflies which  subsequently  developed  displayed  abnormal 
colouration.  Those  that  had  been  reared  at  lower  tem- 
peratures exhibited  approximations  in  colouring  to  allied 
forms  living  in  cold  climates,  while  those  reared  in  excep- 
tional heat  resembled  the  allied  forms  inhabiting  hot  cli- 
mates. They  were  able,  though  only  in  isolated  cases,  to 
show  that  tliis  changed  colouration  was  transmitted  to  the 


118  Heredity,  Disease  and  Human  Evolution 

following  generation.  Does  this  mean,  however,  that  the 
alteration  was  transferred  to  the  germ?  Assuredly  it  has 
no  such  signification.  For  the  pupa  already  contains  the 
germinal  cells  of  the  butterfly  that  is  subsequently  to  de- 
velop, and  it  is  obvious  that  these  cells  may  be  influenced 
by  the  cold  just  as  much  as  the  entire  pupa.  Thereby 
they  are  altered  in  the  same  direction,  and  for  this  reason 
the  offspring  of  the  butterfly  also  exhibit  the  changes  in 
colour. 

In  these  cases,  therefore,  the  inheritance  is  readily 
explicable  through  the  simultaneous  working  of  the  changed 
temperature  upon  parents  and  germ. 

Let  us  take  another  example.  Mice  have  been  bred  at 
an  abnormally  high  temperature  (Sumner,  who  used  a 
temperature  of  79°  F,  and  in  other  cases  a  temperature 
a  little  above  88°  F),  and  it  was  then  observed  that  the 
ears,  tail,  and  feet  were  longer  than  normal,  and  more 
particularly  that  the  hair  became  thinner.  It  might  be 
supposed  that  in  these  cases  also  the  higher  temperature 
had  influenced  the  germinal  cells  as  well  as  the  parental 
bodies,  for  the  offspring  of  these  animals,  although  bred  at 
ordinary  temperatures,  exhibited  the  same  changes.  But 
in  this  case  the  explanation  cannot  be  accepted,  because 
the  body-temperature  of  the  parental  animals  exhibited  no 
increase  in  the  warm  chambers,  so  that  the  increased  tem- 
perature of  the  environment  could  not  exercise  any  in- 
fluence on  the  germinal  cells.  The  animals  were  able  to 
adapt  themselves  to  the  changed  external  conditions,  and, 
by  diminished  heat-production  or  by  increased  heat-loss, 
they  could  keep  their  own  temperature  constant.  How, 
then,  are  we  to  explain  the  inheritance  in  this  case?  We 
have  first  to  ask  how  the  bodily  changes  in  question  came 
about.  It  was  certainly  not  by  a  direct  influence  of  the 
heat  upon  the  skin,  leading  to  the  formation  of  less  hair, 
to  increased  growth  of  the  tail,  etc.,  for  how  could  the 
heat  bring  this  about?  The  only  possible  way  is  that  the 
unusual  heat  evoked  changes  of  some  kind  in  the  body, 


Significance  of  Diseases  to  Offspring  119 

changes  in  metabolism,  and  that  the  transformations  above 
described  were  the  indirect  consequences  of  these  changes. 
Let  us  recall  the  extent  to  which  human  beings,  and  there- 
fore doubtless  other  animals  as  well,  are  affected  by  being 
permanently  kept  in  a  temperature  of  86°  F.  Under  such 
conditions  we  do  not  feel  as  well  as  usual,  this  showing 
that  our  whole  system  has  been  infli^enced  in  some  way. 
There  is  also  observed  an  increased  redness  of  the  skin, 
induced  by  the  action  of  the  nervous  system,  increased 
perspiration,  etc.  In  view  of  these  facts,  we  can  readily 
understand  that  similar  influences  affecting  the  bodies  of 
certain  lower  animals  may  alter  the  conditions  of  growth 
of  the  hair.  If,  however,  these  latter  changes  are  depend- 
ent upon  changes  in  metabolism,  it  is  easy  to  understand 
that  the  chemical  abnormalities  in  question  may  have  a 
similar  effect  upon  the  germinal  cells. 

It  seems  that  this  explanation  is  not  the  only  possible 
one.  "While  actually  engaged  in  writing  this  chapter  I 
learn  that  in  another  series  of  experiments,  in  which  rats 
were  bred  at  a  lower  temperature,  the  animals  were  found 
to  display  a  definite,  if  not  extensive,  depression  in  the 
body  temperature.  It  follows  that  in  Sumner's  experi- 
ments the  germinal  cells  may  have  been  influenced  by  such 
a  reduction  in  the  body  temperature. 

In  any  case,  in  respect  of  these  experiments,  it  is  un- 
necessary to  assume  the  direct  transference  of  the  acquired 
changes  to  the  germinal  cells.  All  that  has  occurred  is 
that  a  simultaneous  influence  has  been  exerted  by  cer- 
tain conditions  upon  the  parental  organism  and  upon  the 
germinal  cells.  We  do  not  mean  that  the  environmental 
influences  have  directly  exercised  this  simultaneous  effect, 
but  that  changes  have  been  induced  in  the  metabolism  of 
the  body,  and  that  these  have  operated  as  indirect  factors 
of  the  simultaneous  changes  in  body  and  germ. 

Another  example  may  be  given.  Kammerer  made  the 
following  experiments.  In  one  series  of  experiments  he 
kept  the  spotted  salamander  for  a  number  of  years  upon 


120  Heredity,  Disease  and  Human  Evolution 

a  yellow  ground ;  in  another  series  he  kept  the  animals 
upon  a  black  ground.  In  the  former  case  the  yellow 
colouration  of  the  salamanders  became  continually  more 
widely  extended,  while  the  black  colouration  diminished  in 
extent,  but  without  disappearing  altogether;  in  the  sala- 
manders kept  upon  a  black  ground  the  areas  of  black  col- 
ouration increased.  It  further  appeared  that  the  offspring 
of  the  animals  had  undergone  corresponding  changes,  those 
of  the  yellower  salamanders  being  much  yellower  than 
usual,  and  those  of  the  blacker  salamanders  much  blacker. 
It  is  obvious,  however,  that  the  yellow  or  black  ground 
cannot  be  supposed  directly  responsible  for  the  transfor- 
mation in  the  skin,  for  this  is  the  result  of  an  internal 
modification  in  the  animal,  induced  by  the  change  in  the 
illumination.  On  the  lighter  ground,  there  is  more  light 
to  influence  the  animal  than  upon  the  darker  ground.  The 
internal  change  thus  induced,  chemical  in  nature,  is  com- 
petent at  the  same  time  to  affect  the  skin  and  change  its 
colour,  and  to  influence  the  germinal  cells  in  a  like  sense. 
As  has  recently  been  shown,  it  is  also  possible  that  the 
stronger  illumination  penetrates  to  the  germinal  cells,  hav- 
ing the  same  effect  in  them  as  in  the  body.  The  influence 
of  the  weaker  illumination  upon  the  darker  ground  natu- 
rally finds  a  similar  explanation. 

Again,  Kammerer  made  remarkable  experiments  with 
the  accoucheur  toad.  In  these  creatures  the  male,  living 
on  land,  wraps  the  fertilised  ova  of  the  female,  filiform  in 
shape  and  ranged  side  by  side,  round  his  hind  legs,  and 
carries  them  about  with  him  for  a  time,  until  the  young 
are  so  far  developed  that  when  the  male  now  enters  the 
water,  they  emerge  as  tadpoles  and  undergo  their  further 
development  in  the  free  state.  But  if  the  females  were 
kept  at  a  higher  temperature  and  in  a  drier  atmosphere  than 
customary,  they  proceeded  to  deposit  their  eggs  in  the 
water,  and  the  eggs  could  no  longer  be  carried  about  by 
the  male,  for  their  development  was  accelerated  under  the 
influence  of  the  water,  and  the  young  animals  very  speed- 


Significance  of  Diseases  to  Offspring  121 

ily  emerged.  After  this  had  happened  for  several  gen- 
erations, the  offspring,  even  when  not  kept  at  an  enhanced 
temperature,  went  straight  to  the  water  when  sexually  ma- 
ture and  laid  their  eggs  there.  At  first  sight  it  might 
seem  as  if  the  changed  custom  had  been  inherited.  But  it 
is  easy  to  see  that  nothing  of  the  kind  had  really  taken 
place.  The  changed  conditions  have  a  primary  influence 
upon  the  eggs  laid  in  the  water,  and  from  these  eggs  are 
derived,  not  only  the  new  generation  of  animals,  but  the 
germinal  cells  originating  in  the  bodies  of  these.  In  such 
conditions  the  habituation  to  the  water  has  its  effect  upon 
the  germinal  cells  as  we41  as  upon  the  young  toads. 

A  general  account  has  now  been  given  of  the  experi- 
mental evidence  as  yet  available  bearing  upon  the  problem 
of  the  inheritance  of  acquired  characters.  It  has  been 
shown  how  extraordinarily  difficult  it  is  to  arrive  at  any 
decisive  conclusion  upon  this  question.  This  much,  how- 
ever, is  certain,  that  no  one  has  hitherto  succeeded  in  prov- 
ing that  acquired  characters  can  be  directly  transferred 
as  such  to  the  germ.  There  is  no  evidence  that  from  the 
changed  organ  something  is  given  off  which  can  enter  the 
germ  and  induce  therein  a  corresponding  change,  or  that 
by  any  other  process  the  acquired  character  can  directly 
or  indirectly  influence  the  germ.  On  these  grounds  we 
can  affirm  to-day  that  the  inheritance  of  acquired  changes 
does  not  occur. 

On  the  other  hand,  however,  it  is  a  well-established  fact 
that  in  many  instances  characters  which  first  made  their 
appearance  in  the  parent  are  to  be  found  in  the  offspring. 
In  such  cases,  there  is  no  inheritance  in  the  strict  sense 
of  the  term.  "What  happens  is  that  in  one  way  or  another 
the  change  is  simultaneously  induced  in  the  parental  body 
and  in  the  germinal  cells  which  it  contains,  so  that  the 
respective  changes  arise  independently.  This  is  possible  in 
two  different  ways.  A  change-inducing  influence  invading 
the  body  may  directly  influence  the  germ  as  well,  as  hap- 
pens in  the  case  of  alcohol  and  of  Rontgen  rays.    On  the 


122  Heredity,  Disease  and  Human  Evolution 

other  hand,  the  environmental  influence  may  first  induce 
some  modification  in  the  body,  a  change  in  some  vital  proc- 
ess, and  this  may  affect  some  particular  part  of  the  parental 
body,  giving  rise  to  the  acquirement  of  a  new  character, 
and  simultaneously  may  influence  the  germ  by  inducing  a 
corresponding  change  in  the  rudiment  of  the  same  organ 
that  is  affected  in  the  parent.  This  process  is  known  as 
parallel  induction. 

It  might  be  supposed  a  matter  of  practical  indifference 
whether  the  appearance  in  the  offspring  of  a  character  ac- 
quired by  the  parent  be  due  to  direct  transmission,  or 
whether  it  be  due  to  an  equivalent  influence  exercised 
upon  parent  and  upon  germ.  As  far  as  the  individual 
child  is  concerned,  the  distinction  is  certainly  of  no  mo- 
ment. If,  however,  we  wish  to  obtain  precise  ideas  about 
heredity,  and  if  we  wish  to  be  able  to  decide  in  individual 
cases  whether  an  acquired  character  may  be  expected  to 
be  reproduced  in  the  offspring,  the  distinction  is  one  of 
very  great  importance. 

On  this  assumption  of  a  simultaneous  influence  on  parent 
and  child,  we  understand  without  further  argument  that 
the  effects  of  injury  and  many  diseases  cannot  be  trans- 
missible by  inheritance.  As  regards  injury,  it  is  clear  that 
in  the  germinal  cells  an  equivalent  injury  to  that  suffered 
by  the  parent  could  only  be  effected  by  an  identical  influ- 
ence exercised  upon  the  rudiment  of  the  organ  concerned. 
For  example,  amputation  of  a  limb  in  the  parent  could  lead 
to  the  absence  of  the  same  limb  in  the  child  only  by  the 
removal  of  that  portion  of  the  germinal  cell  out  of  which 
the  limb  is  destined  to  develop.  For  it  is  inconceivable 
that  the  absence  of  a  limb  could  per  se  exercise  such  an 
influence  upon  the  germ. 

Further,  it  is  easy  to  understand  that  of  acquired  char- 
acters, in  the  narrower  sense,  many  cannot  be  reproduced 
in  the  offspring.  To  give  particular  examples,  the  ac- 
quired enlargement  of  an  athlete's  muscles,  which  often 
attain  to  an  astonishing  size,  is  not  transmissible  to  the 


Significance  of  Diseases  to  Offspring   123 

offspring.  Such  muscular  enlargement  is  the  outcome  of 
voluntary  action,  operating  by  way  of  the  peripheral 
nerves,  whereby  the  muscles  are  repeatedly  and  power- 
fully set  in  action.  In  the  germinal  cells,  a  strengthening 
of  the  muscle-rudiment  could  be  effected  only  by  exercise — 
a  condition  obviously  impossible  to  fulfil.  Again,  it  is 
impossible  for  the  increase  of  any  mental  capacity  to  be 
associated  with  a  corresponding  increase  of  energy  in  the 
appropriate  germinal  rudiment.  We  may  calculate  the 
individual  as  much  as  we  please  in  any  direction,  musical, 
mathematical,  scientific,  or  ethical,  but  this  will  never  exer- 
cise any  such  influence  upon  the  germ  that  the  individual 
subsequently  developing  from  that  germ  will  display  in 
consequence  an  increase  in  the  capacity  that  has  been  espe- 
cially cultivated  by  the  parent.  Technical  capacities  again, 
such  as  the  specialised  manual  dexterity  of  the  pianist,  or 
the  aptitude  for  various  handicrafts  acquired  by  skilled 
workmen,  have  to  be  reacquired  by  the  offspring,  for  they 
are  not  transmitted  by  inheritance.  Indeed,  the  fact  is 
obvious.  How  could  we  otherwise  explain  why  it  is  that 
parents  who  have  specially  trained  their  faculties  in  some 
particular  direction  may  have  children  who  display  no 
conspicuous  ability  along  the  same  lines?  Where  chil- 
dren display  from  youth  upwards  faculties  similar  to  those 
for  which  their  parents  have  been  distinguished,  we  are 
compelled  to  assume,  in  the  light  of  the  present  argument, 
that  they  were  primarily  endowed  in  the  germ  with  the 
rudiments  of  the  same  faculties,  and  that  there  has  not 
been  transmission  of  an  acquired  character  from  the  par- 
ent. 

In  discussions  of  the  theory  of  evolution  the  question 
has  been  mooted  of  the  transmission  from  parents  to  off- 
spring of  qualities  developed  by  practice — of  their  trans- 
mission as  functional  adaptations.  It  has  been  assumed 
that  individual  adaptations  to  new  conditions  can  be  trans- 
mitted by  inheritance.  Here  again,  however,  it  is  our  opin- 
ion that  in  all  the  cases  in  which  the  adaptation  arises 


124  Heredity,  Disease  and  Human  Evolution 

directly  or  through  the  intermediation  of  the  nervous  sys- 
tem, in  all  those,  that  is  to  say,  which  are  not  the  out- 
come of  any  chemical  change  affecting  the  body  as  a  whole, 
the  reappearance  of  the  adaptation  in  the  offspring,  its 
transmission  by  "inheritance,"  is  excluded.  Only  when 
the  external  influence  leads  to  a  change  in  metabolism, 
when  this  leads  to  the  adaptation,  and  when  the  primary 
change  in  metabolism  is  competent  to  exert  an  identical 
influence  upon  the  germinal  cells,  is  it  possible  for  the 
adaptation  to  be  transmitted  to  the  offspring. 

We  see,  then,  that  the  appearance  in  the  offspring  of 
qualities  acquired  by  the  parents  is  limited  to  the  case  of 
those  changes  in  which  it  is  possible  for  the  parental  body 
and  the  germinal  cells  to  be  simultaneously  influenced,  or 
in  which  a  modification  induced  in  the  parental  organism 
is  the  cause  of  the  appearance  of  the  new  quality,  and 
the  modification  in  question  exercises  the  like  influence 
upon  the  germ.  In  both  these  cases  we  have  to  do  with 
parallel  induction,  and  not  with  manifestations  of  hered- 
ity in  the  strict  sense  of  the  term.  The  advocates  of  the 
view  that  acquired  characters  are  inherited  may  very  well 
be  satisfied  with  these  admissions,  for  even  though  ac- 
quired characters  are  not  inherited  in  the  sense  formerly 
believed,  and  still  believed  by  many  to-day,  it  remains  an 
indisputable  fact  that  many  changes  acquired  by  the  par- 
ents do  actually  reappear  in  the  offspring. 

4.    Diseases  Affecting  the  Parents  and  Recurring 

in  the  Children 

('^Hereditary"  Diseases) 

"We  showed  in  the  first  chapter  that  every  morbid  state 
is  characterised  by  a  diminution  in  functional  capacity,  at 
first  of  individual  organs,  and  ultimately  of  the  body  as  a 
whole.  This  impairment  of  functional  activity  is  depend- 
ent upon  anatomical  changes  in  the  organs,  and  these 
changes  are  in  their  turn  induced  by  manifold  injurious 


Significance  of  Diseases  to  Offspring   125 

influences  (poisons,  micro-organisms,  etc.).  We  are  thusj 
led  to  define  disease  as  the  sura-total  of  the  depressions  iuj 
the  vital  processes  resulting  from  alterations  in  the  stmc-( 
ture  of  the  body. 

In  our  consideration  of  the  ''inheritance  of  diseases"  we 
must  start  from  this  definition,  for  it  is  obvious  at  the  out- 
set that  no  hereditary  transmission  occurs  in  the  case  of 
the  depression  in  functional  activity. 

It  is  impossible  that  this  depression  should  be  inherited,  if 
only  for  the  reason  that  the  germinal  cells  do  not  as  yet 
contain  any  functioning  organs,  organs  whose  functions 
are  capable  of  being  disordered ;  and  in  addition  we  have 
to  remember  that  depression  in  functional  activity  is  not 
a  process  existing  per  se,  but  is  one  dependent  upon  the 
anatomical  structure  of  the  organ  whose  function  is  affect- 
ed. •  All  that  is  possible  is  for  the  germs  to  be  influenced 
through  the  occurrence  of  changes  in  the  individual  rudi- 
ments out  of  which  will  subsequently  develop  organs  cor- 
responding with  those  now  diseased  in  the  parent — the  1 
changes  being  of  such  a  nature  that,  owing  to  the  abnor- 
mality of  the  rudiments,  it  will  result  in  the  offspring  that 
alterations  in  the  organs  will  appear  corresponding  with 
those  which  have  now  appeared  in  the  parent.  Then  the 
offspring  will  display  the  same  morbid  phenomena  as  the 
progenitor.  It  follows  that  when  we  speak  of  the  "inher- 
itance of  diseases"  we  mean  no  more  than  this,  that  in 
the  child  like  anatomical  changes  are  found  that  were 
found  in  the  parent,  and  that  in  both  individuals  these 
changes  induce  like  morbid  phenomena.  Hence  it  would 
be  better  to  speak  of  the  inheritance  of  the  anatomical 
changes.  Indeed,  even  the  terms  "inheritance"  and  "he- 
reditary transmission"  are  open  to  objection,  for  their  strict 
significance  is,  in  this  connexion,  that  the  anatomical 
changes  are  transmitted  from  the  parents  to  the  offspring, 
and  this  idea,  as  we  have  seen  before  and  shall  see  again, 
does  not  correspond  with  the  facts  of  the  case.  The  only 
perfectly  objective  method  of  expression  is  to  say  that  off- 


126  Heredity,  Disease  and  Human  Evolution 

spring  and  parent  manifest  like  anatomical  changes,  and 
that  these  induce  like  morbid  phenomena  in  both.  The  use 
of  the  terms  "inheritance"  and  "hereditary  transmission" 
has,  however,  become  habitual,  and  no  objection  need  be 
raised  to  this  usage  provided  we  understand  clearly  what 
we  mean.  But  we  must  never  lose  sight  of  two  facts :  first 
of  all,  that  no  inheritance  really  occurs  in  the  rigid  sense 
of  that  word ;  and  secondly,  that  when  we  speak  of  inher- 
itance we  refer  only  to  the  "inheritance"  or  "hereditary 
transmission"  of  the  anatomical  changes,  and  not  of  the 
actual  diseases.  In  the  discussions  which  follow  it  is  this 
that  we  shall  always  mean  when  for  the  sake  of  brevity 
we  speak  of  the  "inheritance  of  diseases." 

The  actual  method  by  which  the  morbid  disposition  is 
transmitted  from  parent  to  offspring  will  be  considered 
in  a  subsequent  section.  It  is  our  present  concern  to  learn 
what  are  the  diseases  transmissible  by  inheritance.  They 
are  numerous,  though  less  numerous  than  is  currently  sup- 
posed. In  many  cases  in  which  people  speak  of  the  inher- 
itance of  disease  this  has  not  occurred  in  the  sense  above 
defined,  for  inheritance  is  merely  simulated.  What  occurs 
is  not  that  anatomical  changes  corresponding  with  those 
that  induce  the  disease  in  the  parent  affect  the  germinal 
cells,  and  consequently  recur  in  the  offspring,  but  that  j 
the  injurious  influence  which  leads  in  the  parent  to  the  f 
morbid  change  in  question  is  itself  transferred  to  the  off- 
spring, and  in  the  germ  and  in  the  offspring  itself  induces 
like  changes.  To  make  this  distinction  clear  we  must 
briefly  recur  to  the  considerations  detailed  in  an  earlier 
section  (p.  69)  as  to  the  appearance  of  diseases  in  the 
offspring. 

Simulated  inheritance  occurs  in  the  case  of  certain  dis- 
eases induced  by  micro-organisms.  The  most  important  of 
these  is  tuberculosis,  and  to  this  illness  we  shall  now  limit 
the  discussion,  for  the  considerations  that  apply  here  are 
readily  applicable  to  other  infectious  diseases.  In  all  the'Y 
infectious  diseases  in  which  a  simulated  inheritance  takes  % 


Significance  of  Diseases  to  Offspring    127 

place,  what  in  truth  happens  is  that  the  living  organisms 
which  are  the  exciters  of  disease  pass  from  the  parent  to 
the  germ  or  to  the  offspring  and  thus  induce  disease  in  the 
latter.  All  that  really  takes  place  is  an  infection  of  the 
germ. 

We  learned  first  of  all  (p.  72)  that  in  very  rare  in- 
stances tubercle  bacilli  may  penetrate  the  ovum,  which 
nevertheless,  as  is  proved  by  experiments  on  birds,  remains 
capable  of  development.  When,  in  such  cases,  the  offspring 
are  diseased  it  seems  at  first  sight  as  if  the  tuberculous 
processes  had  been  transmitted  by  inheritance,  whereas 
really  the  germ  has  not  undergone  any  corresponding 
changes,  but  merely  contains  the  tubercle  bacilli,  whose 
subsequent  development  in  the  child  gives  rise  to  tuber- 
culous processes. 

Similar  erroneous  conclusions  are  apt  to  be  drawn  in 
the  commoner  cases  in  which  the  body  of  the  developing 
child  is  invaded  by  tubercle  bacilli  derived  from  the  mater- 
nal body  by  way  of  the  placenta.  In  these  cases  also  in- 
heritance is  simulated,  whilst  the  actual  process  is  one  of 
consecutive  infection. 

Tuberculous  changes  as  such  cannot  possibly  be  trans- 
mitted, for  they  are  induced  solely  by  the  action  of  tuber- 
cle bacilli,  and  are  inconceivable  in  default  of  this  action. 

The  second  way  in  which  a  false  impression  may  arise 
is  that  when  tuberculosis  occurs  in  the  offspring  what  has 
been  transmitted  from  the  parents  may  be  nothing  more 
than  a  peculiar  susceptibility  to  the  bacillary  infection. 
If  in  such  cases  the  offspring  are  for  any  reason  (see  p.  73) 
attacked  by  the  bacilli,  the  micro-organisms,  finding  a  suit- 
able soil,  may  often  induce  severe  tuberculous  disease  in 
several  children  of  the  same  family,  and  the.se  children 
are  then  supposed  to  suffer  from  inherited  tuberculosis. 
In  such  cases  what  has  been  transmitted  is  a  predisposition 
to  tuberculosis,  a  predisposition  which  does  not  per  se  in- 
duce the  disease,  and  whose  existence,  in  many  cases,  does 
not  lead  to  any  impairment  of  health. 


128  Heredity,  Disease  and  Human  Evolution 

The  offspring  may,  in  the  third  place,  be  infected  when 
no  inherited  predisposition  to  tuberculosis  exists.  All 
human  beings  are  susceptible  to  this  bacillary  invasion  to 
a  greater  or  less  degree,  although  in  some  the  susceptibility 
is  so  slight  that  they  never  become  seriously  ill.  Those 
children  in  whose  bodies  the  bacilli  are  able  to  flourish,  if 
invaded  by  large  numbers  of  the  micro-organisms,  as  is 
especially  liable  to  happen  in  the  children  of  tuberculous 
parents,  are  apt  to  become  tuberculous  although  there  is, 
in  these  cases,  absolutely  no  hereditary  factor  in  the  causa- , 
tion  of  the  disease.  But  since,  in  such  cases,  the  true 
origin  of  the  illness  may  easily  be  overlooked,  it  is  often 
erroneously  assumed  that  the  disease  is  the  outcome  of 
heredity. 

"We  thus  see  that  there  is  a  series  of  possibilities  whereby 
heredity  may  be  simulated,  so  that  we  are  led  to  regard 
the  number  of  inheritable  diseases  as  being  even  greater 
than  it  really  is. 

If  we  turn  to  consider  the  cases  that  actually  belong  to 
the  hereditary  category,  we  must  first  point  out  that  we 
speak  here  only  of  illnesses  in  the  strict  sense  of  the  term. 
Heredity  also  plays  a  part  in  the  production  of  a  great 
series  of  bodily  changes  which  do  not  lead  to  a  depression 
of  the  functional  activity  of  any  organ  or  to  a  disturbance 
of  the  general  sense  of  wellbeing.  Above  all,  we  have 
to  think  in  this  connexion  of  many  malformations  which, 
although  they  naturally  impair  the  functions  of  the  af- 
fected organs,  need  not  seriously  impair  the  vital  capacity 
of  the  individual,  and  may  leave  it  altogether  unaffected. 

These  malformations  cannot  be  left  out  of  account,  in 
part  because  the>  may  lead  to  the  occurrence  of  morbid 
manifestations,  and  in  part  because  they  furnish  us  with 
extremely  characteristic  examples  of  the  working  of  hered- 
ity. 

It  is  desirable  to  classify  inheritable  morbid  states  in  a 
number  of  groups,  arranged  either  in  accordance  with  the 
changes  affecting  particular  organic  systems,  or  else  in 


Significance  of  Diseases  to  Offspring  129 

accordance  with  certain  peculiarities  of  the  phenomena  of 
inheritance,  a  knowledge  of  which  is  of  great  importance 
to  our  subject.  In  the  theory  of  hereditary  transmission, 
and  also  from  the  practical  point  of  view,  we  are  greatly 
concerned  to  know  whether  diseases  are  transmitted  di- 
rectly from  one  generation  to  the  next,  or  whether  one 
or  more  generations  may  remain  exempt;  whether  they 
invariably  affect  all  the  offspring,  or  some  only;  whether, 
in  the  latter  ease,  the  healthy  and  the  diseased  children 
are  distributed  in  accordance  with  definite  rules;  whether 
the  marriage  of  near  kin  and  the  transmission  of  taint 
from  diseased  ancestors  play  a  part;  and  so  on.  In  the 
present  section  we  shall  touch  on  these  matters  only  in 
passing,  but  they  will  subsequently  be  considered  in  fur- 
ther detail. 

"We  will  speak  first  of  a  group  of  illnesses  in  which  the 
morbid  heredity  is  characterised  by  the  fact  that  the  female 
members  of  the  family  themselves  remain  nearly  or  com- 
pletely free  from  the  disease,  but  transmit  to  their  sons 
the  morbid  taint  they  have  themselves  derived  from  their 
fathers.  Of  course  this  is  possible  only  when  the  women, 
although  they  do  not  themselves  suffer  from  the  disease, 
have  latent  in  their  germinal  cells,  in  their  ova,  changes 
corresponding  to  the  disease  they  transmit.  The  male  mem- 
bers of  the  family,  who  need  not  in  all  cases  themselves 
actually  suffer  from  the  disease,  transmit  it,  not  to  their 
sons,  but  to  their  grandsons,  through  the  intermediation 
of  their  daughters. 

The  best  example  of  heredity  of  this  type  is  afforded 
by  the  disease  known  as  hemophilia,  or  the  hemorrhagic 
diathesis,  a  morbid  condition  characterised  by  the  pecu- 
liarity that  wounds,  or  even  very  trifling  wounds,  are  apt 
to  lead  to  serious  and  it  may  be  fatal  loss  of  blood.  The 
actual  determining  cause  of  the  excessive  bleeding  is  not 
fully  understood ;  but  it  appears  probable  that  the  trouble 
is  dependent  upon  deficient  coagulability  of  the  blood,  in 


130  Heredity,  Disease  and  Human  Evolution 

consequence  of  which  the  cut  or  lacerated  blood-vessels  are 
not  closed  quickly  enough  by  blood-clots. 

In  a  small  percentage  of  instances  women  are  also  af- 
fected with  the  disease,  but  some  investigators  dispute  this 
assertion,  contending  that  the  cases  in  which  women  have 
appeared  to  be  "  bleeders ' '  can  be  explained  in  some  other 
way. 

Hemophilia  is  not  a  common  disease,  but  it  has  re- 
ceived especial  attention  owing  to  its  striking  and  alarm- 
ing consequences.  This  explains  why,  in  their  Treasury  of 
Human  Inheritance,  Bullock  and  Fildes  were  able  to  give 
two  hundred  and  forty  genealogical  trees  of  bleeder  fam- 
ilies, trees  varying  greatly  in  comprehensiveness.  In  rare 
instances  only  has  the  course  of  such  families  been  followed 
for  so  many  generations  as  in  the  case  of  the  bleeders  of 
Tenna  and  in  that  of  the  Mampel  family,  Tenna  is  a 
village  in  the  Swiss  canton  of  Orisons.  The  reports  of  the 
bleeders  in  this  locality  go  back  to  the  end  of  the  seven- 
teenth century,  and  comprise  seven  generations.  E.  Zahn 
makes  this  family  history  the  foundation  of  his  novel  Die 
Frauen  von  Tanno. 

The  Mampel  family,  whose  records  were  last  examined 
by  Lossen,  comprised  217  members.  Of  the  121  males,  37 
were  bleeders;  the  97  women  were  all  exempt. 

A  remarkable  peculiarity  of  bleeder  families,  and  one  to 
which  we  shall  return,  is  their  exceptional  fertility,  accom- 
panied by  an  exceptionally  high  child  mortality. 

Another  morbid  condition,  transmitted  in  a  singular  way 
to  hemophilia,  is  colour-blindness,  the  sufferers  from  which 
are  either  totally  unable  to  distinguish  colours,  or  con- 
fuse certain  colours,  and  especially  red  and  green.  We 
have  numerous  genealogical  trees  displaying  the  incidence 
of  colour-blindness.  In  these,  the  proportion  of  women  af- 
fected with  the  disease  is  somewhat  variable,  but  on  the 
average  we  find  15  men  suffering  from  colour-blindness  for 
every  one  woman  similarly  affected. 

Exemption  of  the  female  members  in  affected  families 


Significance  of  Diseases  to  Offspring  131 

is  also  observed  in  hemeralopia,  or  night-blindness,  which 
however  is  usually  transmitted  by  direct  inheritance  (see 
the  next  group).  Those  suffering  from  night-blindness  see 
very  badly  in  twilight  and  in  moonlight. 

As  regards  progressive  muscular  atrophy,  a  case  has  also 
been  recorded  in  which  inheritance  took  place  on  similar 
lines.    But  here,  too,  direct  inheritance  is  the  rule. 

In  the  case,  on  the  other  hand,  of  a  large  proportion  of 


Fig.  5. — Genealogical  Tree  of  the  Mampel  family  of  bleeders  (after 
Lessen).  Tlie  circles  indicate  the  female  and  the  squares 
the  male  members  of  the  family.  The  black  squares  denote 
the  bleeders. 

the  families  affected  with  congenital  optic  atrophy  (optic 
neuritis),  exemption  of  the  female  members  from  the  dis- 
ease has  been  observed,  while  they  transmit  it  to  their  sons ; 
but  in  some  of  the  families  with  this  morbid  inheritance,  a 
small  percentage  of  the  female  members  themselves  suffer 
from  the  disease. 

The  explanation  of  this  peculiar  form  of  inheritance  is 
far  from  easy,  and  the  question  is  certainly  too  difficult 
for  discussion  here. 

In  a  second  group  of  illnesses,  we  find  a  certain  num-  \ 
ber  of  examples  of  direct  inheritance  (inheritance,  that  is  \ 


132  Heredity,  Disease  and  Human  Evolution 

to  say,  without  skipping  a  generation),  in  which  the  mor- 
bid manifestations  appear  alike  in  male  and  female  mem- 
bers of  the  family,  and  may  be  transmitted  by  these  to 
both  sexes  in  the  next  generation.  It  is,  however,  very 
important  to  note  that  the  morbid  heredity  does  not  affect 
all  the  children,  but  only  about  one  half  of  these,  and 
this  matter  must  be  considered  more  fully  in  the  next 
section.  In  these  cases,  if  the  child  of  a  diseased  parent 
remains  exempt  from  the  disease,  the  morbid  heredity  is 
interrupted  at  this  point,  for  the  offspring  of  this  child 
are  also  free  from  the  taint. 

A  very  characteristic  and  unusually  comprehensive  ex- 
ample is  afforded  by  the  celebrated  family  history  studied 
by  Nettleship.  Here  the  incidence  of  night-blindness  in  the 
Nougaret  family  is  recorded  for  ten  generations,  the  rec- 
ords beginning  with  the  year  1637.  Reports  are  available 
regarding  2,116  members  of  this  family,  of '  whom  135 
suffered  from  night-blindness,  the  cases  being  distributed 
among  males  and  females  in  about  equal  proportions. 

In  a  case  of  malformation  of  the  fingers  reported  by 
Farabee  the  inheritance  of  the  affection  took  a  similar 
course.  The  fingers  contained  two  phalanges  only.  The 
anomaly  was  transmitted  to  one  half  the  children  of  both 
sexes,  and  the  offspring  of  the  normal  individuals  remained 
unaffected. 

The  same  course  of  heredity  has  been  observed  in  cases 
of  congenital  cataract. 

The  third  group  of  affections  comprises  the  congenital 
malformations:  hare-lip,  Polydactyly,  the  so-called  cleft- 
hand  and  other  developmental  abnormalities  of  the  hand, 
web-toes,  a  case  of  absence  of  the  sweat-glands.  Here  in- 
heritance is  often  direct,  but  in  different  branches  of  the 
same  family  the  malfonnation  may  appear  in  children 
whose  parents  are  themselves  exempt.  This  is  explicable  on 
the  ground  that  the  grandparents  or  remote  progenitors 
were  affected  with  the  anomaly,  which  has  remained  latent 
in  all  or  some  of  the  members  of  one  or  more  generations. 


Significance  of  Diseases  to  Offspring   133 

A  fourth  group  consists  of  a  number  of  affections  of  the 
skin.  First  of  all  must  be  mentioned  tjdosis  palmaris,  an 
irregular  thickening  of  the  skin  of  the  palms  of  the  hands 
and  the  soles  of  the  feet.  Cases  have  been  recorded  in 
which  this  affection  was  markedly  hereditary.  To  the 
same  group  belongs  albinism,  characterised  by  an  absence 
of  pigment  from  the  skin,  varying  greatly  in  extent,  in 
the  form  of  pigment-free  macules  isolated  or  in  groups  on 
certain  preferred  parts  of  the  body.  The  condition  is  nat- 
urally most  conspicuous  in  the  coloured  races,  and  here, 
by  contrast,  the  pigment-free  macules  appear  perfectly 
white.  In  a  monograph  on  the  subject  by  Karl  Pearson 
and  others,  a  case  is  recorded  in  which  the  anomaly  was 
transmitted  for  five  generations.  In  one  of  these  genera- 
tions, consisting  of  six  children,  three  only  were  affected. 
To  this  case,  and  to  another  of  the  kind,  we  shall  recur  in 
the  following  chapter.  We  must  also  mention  here  the 
condition  known  as  onychogryphosis,  a  claw-like  formation 
of  the  nails  of  the  fingers  and  toes,  which  in  one  case  has 
been  observed  in  brothers  and  sisters,  the  mother,  a  daugh- 
ter, and  a  granddaughter;  hypertrichosis,  an  excessive 
growth  of  the  hair,  as  seen  in  the  so-called  "hairy  men" 
and  "hairy  women";  hypotrichosis,  or  deficient  growth  of 
the  hair,  to  be  considered  later ;  a  skin-disease  known  as 
psoriasis;  and  finally  xeroderma  pigmentosum,  to  which 
also  we  shall  return. 

In  a  fifth  group,  we  find  certain  inheritable  anomalies  \ 
of  the  eyes,  including  congenital  opacity  of  the  cornea,  | 
shortsightedness,  pigmentary  atrophy  of  the  retina,  glau- 
coma, and  two  conditions  to  which  reference  has  been  made . 
above,  congenital  cataract  and  colour-blindness. 

A  sixth  group  comprises  affections  of  the  nervous  system.  ' 
To  this  category  belong  hysteria,  neurasthenia,  wordblind- 
ness,  Huntington's  chorea,  hereditary  ataxia,  congenital 
myotonia,  and  trophic  edema — diseases  some  of  which  are 
so  exceedingly  rare  that  it  is  needless  here  to  do  more  than 
mention  their  names.     More  important  is  the  hereditary 


134  Heredity,  Disease  and  Human  Evolution 

transmission  of  deafmutism,  of  which  numerous  instances 
are  recorded,  and  which  may  appear  in  certain  families 
with  extraordinary  frequency.  The  work  previously 
quoted,  A  Treasury  of  Human  Inheritance,  gives  a  gene- 
alogical tree  of  83  members,  of  which  53  were  deafmutes. 
Mental  disorders  are  often  encountered  in  association  with 
deafmutism,  a  matter  to  be  discussed  presently.  It  must 
also  be  noted  that  in  the  families  in  which  deafmutism 
is  prevalent,  the  marriage  of  near  kin  is  of  common  oc- 
currence. To  this  we  shall  return.  Among  the  inheritable 
diseases  of  the  nervous  system  must  finally  be  mentioned 
tetany. 

We  come  now  to  the  seventh  group,  one  of  especial  im- 
portance, that  of  the  mental  disorders.  In  these,  as  every 
layman  knows,  heredity  plays  a  great  part.  The  alienist, 
when  examining  his  patients,  never  fails  to  enquire  about 
hereditary  taint,  and  it  is  therefore  not  surprising  that 
we  should  possess  numerous  detailed  and  characteristic 
studies  of  the  inheritance  of  mental  disorders,  illustrated 
by  genealogical  trees.  A  few  examples  may  be  given.  A 
well-known  instance  is  that  of  the  family  Zero,  which  lived 
in  a  secluded  Alpine  valley.  The  founder  of  the  family 
sprang  from  progenitors  not  known  to  be  affected  with 
mental  disorder,  but  was  an  alcoholic.  He  married  a 
woman  belonging  to  a  family  of  Italian  vagrants  who 
traded  in  tinkers'  wares.  This  was  in  the  beginning  of  the 
17th  century,  and  among  their  numerous  descendants  nor- 
mal individuals  were  altogether  exceptional.  In  many 
families,  indeed,  there  w^as  not  to  be  found  a  single  normal 
member.  In  a  number  of  cases  a  considerable  portion  of 
the  offspring  died  in  childhood.  The  manifestations  of 
mental  disorder  were  very  variable.  Some  were  alcoholics ; 
especially  common  were  asocial  individuals,  persons  unable 
to  adapt  themselves  to  the  normal  conditions  of  social  life ; 
there  were  criminals  (sometimes  exhibiting  marked  mental 
disorder),  imbeciles,  idiots,  cripples,  mental  invalids  of 
various  kinds.    In  some  branches  of  the  family,  those  with 


Significance  of  Diseases  to  Offspring   135 

conspicuous  mental  disorder  predominated;  in  others,  the 
asocial  types.  The  founder  of  the  family  had  a  brother 
and  several  cousins  who  were  themselves  normal  and  who 
married  normal  wives.  The  offspring  of  these  marriages 
were  perfectly  healthy. 

As  far  as  mental  disorders  are  concerned,  the  heredity 
of  these  is  greatly  aggravated  by  intermarriage  between 
closely  connected  families,  or  between  those  affected  with 
like  taint.  This  matter  will  require  further  attention.  We 
possess  a  genealogical  tree  showing  that  the  parents  of  a 
woman  suffering  from  mental  disorder  were  themselves 
mentally  abnormal.  They  were  not  blood-relatives,  but 
the  families  of  both  had  exhibited  hereditary  taint  for 
several  generations.  In  the  mother's  case  this  taint  was 
especially  severe.  She  herself  was  mentally  abnormal,  and 
drank  to  excess;  her  father  was  a  drinker,  and  her  pater- 
nal grandfather  a  drinker  who  committed  suicide.  This 
grandfather  had  seven  children,  two  of  whom  died  in  in- 
fancy, while  the  others  were  all  abnormal. 

Another  genealogical  tree  deals  chiefly  with  the  heredi- 
tary transmission  of  epileptic  states  of  varying  severity, 
associated  in  some  cases  with  more  or  less  pronounced 
mental  disorder.  A  marriage  took  place  between  first  cous- 
ins, both  of  whom  were  themselves  abnormal,  while  the 
wife's  parents  were  epileptic.  This  pair  had  six  children, 
of  whom  some  were  eccentric,  some  affected  with  epilepsy 
and  mental  disorder,  and  some  exhibited  bodily  deficiencies. 
In  another  branch  of  the  same  family,  in  which  in  the 
course  of  five  generations  marriages  between  cousins  took 
place  five  times,  there  occurred  such  an  accumulation  of 
epileptic  taint  that  the  six  children  of  the  third  genera- 
tion were  all  epileptics. 

An  eighth  group  of  inheritable  affections  comprises  the  v 
well-known  disorders  of  metabolism,  gout,  obesity,  and  dia-  \ 
betes.     As  regards  the  last-named,  in  especial,  we  have 
genealogical  trees   showing  that  among  the  offspring  of 
diabetics  a  proportion  only,  and  often  not  more  than  half, 


136  Heredity,  Disease  and  Human  Evolution 

are  diseased.     To  this  point  we  shall  return  in  the  next 
section. 

To  a  ninth  group  belong  the  inheritable  tumours,  among 
which  must  be  included  the  so-called  nemofibromata,  mul- 
tiple enchondromata  and  bony  tumours,  fatty  tumours,  con- 
genital malignant  tumours  of  the  eye,  and  to  a  minor  de- 
gree also  cancer  (carcinoma).  So  far  as  we  possess  suffi- 
cient observations,  it  appears  that  inheritance  in  these 
cases  is  usually  direct.  What  is  transmitted,  however, 
is  not  the  tumour  as  such,  but  probably  certain  disturb- 
ances in  the  development  of  the  embryo  which  at  some 
subsequent  period  of  life  lead  to  the  appearance  of  the 
new  growth. 

In  a  tenth  and  last  group  may  be  classed  certain  diseases  / 
which  are  unrelated,  and  whose  only  common  link  is  that  ' 
they  are  all  transmissible  by  inheritance.  These  are  poly- 
aria  (diabetes  insipidus),  characterised  by  the  evacuation 
of  excessive  quantities  of  urine,  alcaptonuria  (which  will 
be  considered  in  the  following  section),  cretinism,  eosino- 
philia  (a  disease  characterised  by  abnormal  behaviour  of 
the  white  blood-corpuscles),  and  certain  diseases  of  the 
blood-vessels  (the  so-called  calcareous  degeneration  of  the 
arteries,  and  the  tendency  of  the  veins  to  undergo  abnor- 
mal enlargement  leading  to  the  formation  of  piles  and 
varices). 

This  concludes  our  general  sketch  of  the  diseases  trans- 
missible by  inheritance.  The  mode  of  transmission  has  al- 
ready been  partially  discussed,  and  will  be  further  con- 
sidered in  the  sequel. 

5.     Rules  in  Accordance  with   Which  Diseases  Affecting 
the  Parents  Make  Their  Appearance  in  the  Children 

In  the  previous  section,  and  also  in  the  sixth  chapter, 
reference  was  made  to  the  fact  that  hereditary  diseases  do 
not  usually  appear  in  all  the  offspring  of  affected  persons ; 
and  that,  further,  whole  generations  may  be  skipped,  so 


Significance  of  Diseases  to  Offspring   137 

that  while  the  children  themselves  remain  healthy  the  dis- 
ease may  he  inherited  by  the  grandchildren.  How  are  such 
exemptions  possible? 

When  parents  are  affected  with  some  abnormal  condition, 
it  might  appear  at  first  sight  that  if  the  changes  were  pres- 
ent in  the  germinal  cells  at  all  they  would  be  present  in 
all  of  these,  so  that  all  the  offspring  of  the  affected  par- 
ents would  necessarily  suffer  from  the  disease.  The  first 
and  most  obvious  objection  to  such  a  notion  is  this,  that 
the  conjugation  of  a  diseased  germinal  cell  with  a  healthy 
one  may  result  in  the  suppression  of  the  morbid  character 
by  the  normal,  so  that  the  offspring  will  remain  healthy. 
There  can  be  no  doubt  that  such  a  process  plays  a  part 
in  producing  exemption,  but  we  are  hardly  justified  in 
assuming  that  herein  lies  the  sole  explanation  that  some  of 
the  children  almost  invariably  escape. 

There  is  another  explanation  which  brings  us  much 
closer  to  the  facts.  We  need  merely  assume  that  not  all 
the  germinal  cells  of  a  diseased  parent  need  necessarily  be 
affected.    But  how  can  this  be? 

In  certain  cases  the  exemption  of  some  of  the  offspring 
may  be  supposed  to  depend  upon  this,  that  the  injurious 
influence  which  gave  rise  to  the  change  in  the  germinal 
cells  had  not  yet  come  into  operation  at  the  time  when 
the  first  members  of  the  family  were  procreated.  If  we 
think,  for  example,  of  chronic  alcoholic  intoxication,  we 
shall  recall  that  a  man  or  a  woman  may  not  take  to  drink 
until  some  time  after  marriage.  The  first  children  would 
then  be  healthy,  and  all  the  later  ones  diseased.  But  such 
occurrences  are  exceptional,  and  as  a  rule  we  cannot  dem- 
onstrate that  exemption  takes  this  course.  Healthy  and 
diseased  children  often  alternate,  though  the  alternation  is 
not  necessarily  a  regular  one. 

Another  explanation  that  has  been  offered,  to  the  effect 
that  the  injurious  influences  operating  on  the  reproduction 
glands  have  been  brought  to  bear  on  some  only  of  the 
germinal  cells,  while  others  have  remained  exempt  from 


138  Heredity,  Disease  and  Human  Evolution 

the  influences,  is  inacceptable.  The  conditions  of  existence 
of  the  germinal  cells  within  the  reproductive  glands  are 
in  the  main  identical,  and  we  cannot  conceive  how  a  por- 
tion of  the  cells,  say  a  half  of  these,  could  escape  when 
the  others  were  injured. 

Moreover,  both  the  interpretations  last  suggested  are  ap- 
plicable to  those  diseases  only  which  first  make  their  ap- 
pearance in  the  body  functionally  competent  for  reproduc- 
tion, and  have  no  bearing  upon  the  origin  of  those  diseases 
which  derive  from  earlier  generations.  When  a  human 
being  inherits  a  disease,  we  seem  at  first  sight  forced  to 
assume  that  all  his  germinal  cells  will  also  be  affected,  in 
the  absence  of  special  conditions  leading  to  the  exemption 
of  some  of  these  cells.  For,  as  we  showed  on  p.  104,  the 
germinal  cells  as  well  as  the  individual  within  whose  body 
they  are  found  are  derived  from  the  same  diseased  ger- 
minal cell  of  the  parent.  But  if  all  the  germinal  cells  are 
affected,  all  the  offspring  must  be  diseased.  Since  some 
of  the  offspring  remain  exempt,  we  are  logically  forced  to 
infer  that  a  portion  of  the  germinal  cells  has  remained 
healthy.  How  can  this  be  explained?  The  following  con- 
siderations will  render  the  matter  intelligible.  We  may 
conceive  that  in  the  process  of  fertilisation  a  diseased  ger- 
minal cell  unites  with  a  healthy  one,  and  that  in  the  con- 
junction between  the  altered  organ-rudiment  of  one  cell 
and  the  normal  organ-rudiment  of  the  other  there  is  not 
produced  an  inseparable  unity,  but  that  both  the  organ- 
rudiments,  the  altered  and  the  normal,  remain  side  by 
side  but  distinct  in  the  primary  germinal  cells  of  the  child 
that  proceed  from  the  fertilised  ovum.  We  must  fur- 
ther assume  that  in  the  formation  of  the  ova  or  spermato- 
zoa that  are  ultimately  derived  from  these  primary  ger- 
minal cells,  the  two  distinct  rudiments  separate  each  from 
the  other,  so  that  there  are  now  produced  certain  ova  (or 
spermatozoa)  affected  with  the  alteration,  and  certain  oth- 
ers that  are  exempt  from  it.  In  that  case,  some  of  the 
children  proceeding  from  these  cells  would  be  healthy,  and 


Significance  of  Diseases  to  Offspring   139 

some  of  them  would  be  diseased,  in  about  equal  propor- 
tions. 

These  considerations  are  not  based  solely  upon  theoreti- 
cal deductions.  They  appear  to  be  justified  by  the  experi- 
ments which  have  of  late  years  been  carried  on  on  the 
lines  laid  down  by  Mendel,  and  they  form  an  essential  part 
of  the  doctrine  known  as  Mendelism.  We  cannot  consider 
Mendelism  in  detail,  but  it  is  necessary  to  our  argriment 
that  we  should  give  a  brief  summary  of  its  most  impor- 
tant data.^ 

As  Mendel  showed,  if  we  cross  certain  plants  of  the 
same  species,  one  variety  bearing  red  flowers  and  the  other 
white,  in  many  instances  the  result  is  one  which  is  of 
especial  interest  to  us  here,  namely  that  all  the  offspring 
in  the  first  generation  have  red  flowers.  The  red  colour  is 
then  said  to  dominate  the  white,  the  bearing  of  red  flowers 
is  called  a  dominant  character.  If  the  red-flowering  plants 
of  this  first  generation  are  now  allowed  to  interbreed,  we 
find  that  75  per  cent,  of  the  next  generation  have  red  flow- 
ers and  25  per  cent,  white.  There  has  thus  occurred  in 
the  second  generation  a  segregation  of  characters ;  the  red- 
flowering  and  white-flowering  tendencies,  which  were  com- 
bined in  the  red-flowering  plants  of  the  previous  genera- 
tion, have  separated  again.  This  is  not  difficult  to  com- 
prehend, but  how  can  we  explain  the  percentage  distribu- 
tion? In  order  to  understand  this  we  must  get  a  clear 
idea  of  the  relationships  that  obtain  in  connexion  with  the 
segregation.  The  plants  of  the  original  red-flowering  vari- 
ety produced  germinal  cells  containing  only  a  red-flowering 
rudiment,  while  the  plants  of  the  white-flowering  variety 
produced  germinal  cells  containing  only  a  white-flowering 
rudiment;  or,  to  condense  the  expression,  the  former  have 
red  germs  only,  the  latter  nothing  but  white.     When  the 

*  For  the  detailed  study  of  this  subject  consult  Bateson,  Mendel's 
Principles  of  Heredity,  1909,  and  Punnett's  Mendelism,  1911.  Re- 
cent German  authorities  are:  Haecker,  AUgemeine  Vcrcrhungslehre, 
1911;  Goldschmidt,  EinfUhrung  in  die  Vererbungswissenschaft,  1911. 


140  Heredity,  Disease  and  Human  Evolution 

plants  are  crossed,  in  the  act  of  fertilisation  a  red  germ 
unites  in  every  case  with  a  white  germ,  and  since  the  red 
germ  is  dominant,  all  the  plants  of  the  next  generation  are 
red.  The  germinal  cells  of  the  red  plants,  however,  at  the 
time  when  these  cells  begin  to  be  formed,  contain  both  red 
and  white  rudiments,  each  germ  is  constructed  out  of  red 
and  white.  When,  subsequently,  the  true  male  and  female 
reproductive  cells  proceed  from  these  primary  germinal 
cells,  a  segregation  of  the  red  and  white  characters  ensues, 
so  that  there  arise  germs  which  are  all  monochrome,  red 
germs  and  white  germs  in  equal  numbers.  In  order  to 
make  it  clear  how  the  percentage  of  red-flowering  and 
white-flowering  plants  comes  to  be  that  above  described,  the 
following  assumption  is  necessary.  In  the  crossing  of  the 
monochrome  germs  (some  white  and  others  red)  of  the 
red  plants  of  the  first  generation,  one  fourth  of  the  red  fe- 
male germinal  cells  combined  with  one  fourth  of  the  red 
male  germinal  cells  to  give  rise  to  red-flowering  plants,  and 
one  fourth  of  the  white-flowering  female  germinal  cells 
united  also  with  one  fourth  of  the  white  male  germinal 
cells  to  produce  white-flowering  plants.  The  remaining  50 
per  cent,  of  the  germs  united  in  such  a  way  that  in  each 
case  a  red  and  a  white  germ  effected  conjugation,  and  the 
result  of  these  unions,  since  the  red  character  is  dominant, 
was  to  produce  red  plants  only.  The  total  outcome,  there- 
fore, is  75  per  cent,  of  red-flowering  and  25  per  cent,  of 
white-flowering  plants. 

If  the  first  mentioned  25  per  cent,  red-flowering  plants 
of  the  second  generation  now  breed  only  with  one  another, 
the  outcome  of  these  unions,  since  the  plants  in  question 
possess  nothing  but  red  germs — for  they  were  produced  by 
the  conjugation  of  a  red  male  with  a  red  female  germinal 
cell — is  red-flowering  plants  and  nothing  else.  For  the 
same  reason,  the  25  per  cent,  of  white-flowering  plants  . 
when  these  are  bred  true,  produce  in  the  next  generation 
white-flowering  plants  only.  The  50  per  cent,  red-flower- 
ing plants,  however,  which  proceeded  from  the  union  of 


Significance  of  Diseases  to  Offspring  141 


red  and  white  germs,  and  which  flower  red  because  the 
red  character  is  dominant,  will,  if  bred  true,  produce  the 
same  sort  of  offspring  as  did  the  red  plants  that  were  the 
outcome  of  the  first  crossing,  namely  75  per  cent,  red-flow- 
ering and  25  per  cent,  white-flowering. 

A  study  of  Fig.  6  should  make  what  has  just  been  said 
somewhat  clearer.  The  large 
circles  represent  the  fully  de- 
veloped plants,  the  small  ones 
germinal  cells.  The  vertical 
striation  indicates  the  red  col- 
our. At  F  we  see  a  striated 
(red)  and  a  white  plant,  side 
by  side.  Each  contains  an  ap- 
propriate germinal  cell.  At 
a  these  cells  conjugate.  From 
the  results  of  conjugation 
there  proceed  at  b  new  gei*m- 
inal  cells,  of  which  each  has 
half  only  seriated  to  show 
that  it  is  a  composite  of  red 
and  white.  From  these  germs 
there  arise  at  c  new  individ- 
uals (comprising  the  first 
daughter  -  generation  FJ, 
which  are  striated  (red)  be- 
cause red  is  dominant.  With- 
in these  new  individuals  we 
see  at  d  that  new  germs  have 
been  formed  in  which  separa- 
tion of  the  colours  has  occurred,  so  that  half  of  them  are 
red  and  half  white.  We  show  in  the  diagram  four  genns 
in  each  individual.  At  e  conjugation  takes  place,  the  red 
and  the  white  germs  from  the  respective  individuals  en- 
countering one  another  in  ways  imposed  by  their  respec- 
tive members.  The  result  of  the  four  acts  of  conjugation  is 
to  give  rise  to  four  new  plants  of  the  second  daughter-gen- 


FlG. 


6. — Memleliaii  Inheritance. 
Explanation  in  Text. 


142  Heredity,  Disease  and  Human  Evolution 

eration  F^,  three  of  these  being  red  and  one  white.  One 
of  the  red  individuals  has  red  germs  only;  the  other  two 
red  individuals  have  red- white  germs  (as  at  b  and  c). 

What  has  been  said  of  red  and  white  applies,  mutatis 
mutandis,  to  other  characters,  such  as  the  shape  of  the 
leaves,  the  size  of  the  seeds,  etc.  Two  such  different  char- 
acters may  unite  just  as  do  the  colours,  and  may  then 
undergo  segregation  in  the  same  percentage  relationships 
as  did  these.  What  occurs  in  respect  of  normal  qualities  is 
also  conceivable  as  regards  the  union  between  a  healthy 
quality  and  the  corresponding  pathological  quality.  In  the 
latter  case,  also,  it  is  conceivable  that  if  the  illness  be  a 
dominant  character,  75  per  cent,  of  the  offspring  will  be 
diseased  and  25  per  cent,  healthy. 

Bearing  on  pathology  another  experiment  is  of  inter- 
est. If  the  red-flowering  plants  of  the  first  generation  are 
crossed  with  pure  white-flowering  plants,  that  is  to  say, 
with  plants  whose  germs  are  all  white,  half  of  the  result- 
ing offspring  are  white  and  half  are  red.  The  explanation 
of  this  is  simple.  As  we  showed  above,  one  half  of  the 
germs  contained  by  the  red-flowering  plants  are  red  and 
the  other  half  are  white,  but  all  the  germs  contained  by 
the  white-flowering  plants  are  white.  In  the  process  of 
fertilisation,  every  red  germ  unites  with  a  white  germ  from 
the  other  plant,  and  since  red  is  a  dominant  character,  the 
offspring  of  these  unions  are  all  red.  The  white  germs  of 
the  red-flowering  plants,  on  the  other  hand,  unite  with 
white  germs  from  the  other  plant,  and  the  offspring  of 
these  unions  are  naturally  white. 

These  results  also  are  applicable  to  the  ease  of  disease. 
When  diseased  individuals  unite  with  healthy  ones  in  the 
act  of  procreation,  it  may  happen,  if  the  disease  is  a  domi- 
nant character,  that  all  the  offspring  are  diseased.  Within 
these  individual  offspring,  however,  there  may  be  produced, 
by  a  process  of  segregation,  both  diseased  and  healthy 
germs;  and  if  the  individual  whose  body  contains  these 
germs  unites  in  marriage  with  a  healthy  person,  of  the 


Significance  of  Diseases  to  Offspring  143 


offspring  of  this  pair  one  half  only  will  manifest  the  dis- 
ease, while  the  other  half  will  remain  healthy. 

The  separation  of  the  healthy  rudiment  from  the  ab- 
normal is  easier  to  understand  than  that  of  the  rudiments 
of  the  red  and  the  white  colouration,  or  those  of  other 
physiological  qualities.  For,  as  regards  these  latter,  it  is 
conceivable  that  a  permanent 
and  intimate  mingling  of  the 
two  characteristics  might  oc- 
cur, so  that  no  process  of  seg- 
regation need  subsequently 
ensue.  Mendel  found  in  the 
case  of  certain  plants  that 
when  white-flowering  and 
red-flowering  varieties  are 
crossed,  the  plants  of  the  first 
crossed  generation  produce 
flowers  that  are  not  red,  but 
pink,  that  is  to  say  are  the 
outcome  of  an  equal  mingling 
of  red  and  white.  Such  a  re- 
sult, however,  is  not  perma- 
nent, for  in  the  second  gen- 
eration a  partial  separation 
of  characters  occurs:  25  per 
cent,  of  the  plants  of  this  gen- 
eration bear  red  flowers,  25 
per  cent,  white,  and  50  per 
cent,  pink ;  and  when  the  red- 
flowering  plants  of  this  gen- 
eration are  now  bred  with  one  another,  these  same  results 
are  repeated  in  the  succeeding  generation.  Thus  a  portion 
of  the  plants  always  remains  mixed.  In  Fig.  7  we  have  a 
diagrammatic  representation  of  these  relationships,  similar 
to  that  given  in  Fig.  6  of  the  inheritance  of  a  dominant 
character.  The  same  lettering  is  used  in  both  figures,  so 
that  it  is  needless  to  give  another  detailed  explanation. 


Fig. 


#'#® 


7. — Meudelian  Inheritance. 
Explanation  in  Text. 


144  Heredity,  Disease  and  Human  Evolution 

The  chief  difference  between  the  two  figures  is  that  in 
Fig.  7  the  intermediate  or  pink  colouration  is  indicated  by 
a  striation  with  wider  interspaces.  Thus  we  show  that  the 
individuals  at  c  and  d  exhibit  a  pink  colouration,  and  in 
the  bottom  row  of  individuals,  at  Fo,  the  two  intermediate 
specimens  are  also  pink.  The  behaviour  of  the  germinal 
cells  is  precisely  similar  to  that  which  occurs  in  Fig.  6.  In 
the  case  of  diseases,  we  cannot  recognise  any  such  mingling 
of  characters  as  may  occur  where  the  colours  of  flowers 
are  concerned.  Indeed  in  the  former  case  we  could  not 
readily  anticipate  that  any  such  intimate  admixture  could 
occur.  It  would  be  difficult  for  a  healthy  rudiment  to  enter 
into  close  combination  with  a  diseased  rudiment.  More 
easily  than  in  the  case  of  the  colour-rudiments  the  dis- 
eased rudiment  and  the  healthy  rudiment  would  remain 
distinct  though  side  by  side,  and  would  thus  be  more  liable 
to  separate  once  more. 

The  question  now  arises  whether  these  theoretical  con- 
siderations do  really  apply  to  the  case;  whether,  that  is 
to  say,  a  separation  of  the  normal  from  the  morbid  rudi- 
ment actually  occurs;  and,  in  especial,  whether  the  phe- 
nomena of  disease-inheritance  display  similar  percentage 
relationships  with  those  that  obtain  in  Mendelian  experi- 
ments. 

Numerous  investigations  have  recently  been  made  to 
throw  light  upon  this  problem.  It  must  first  be  pointed 
out  that  in  the  inheritance  of  disease  a  segregation  of  char- 
acters obviously  occurs.  We  have  repeatedly  drawn  atten- 
tion to  the  fact  that  it  is  quite  exceptional  for  all  the  chil- 
dren of  diseased  parents  to  be  themselves  also  diseased. 
As  a  rule,  a  part  only  of  the  offspring  is  affected.  It  is, 
however,  extremely  difficult  to  ascertain  whether  the  per- 
centage relationships  between  the  healthy  individuals  and 
the  diseased  correspond  with  Mendelian  rules.  On  this 
matter  also  we  have  numerous  reports. 

First  of  all  it  is  evident  that  the  numerical  relationships 
must  depend  upon  the  respective  constitutions  of  the  par- 


Significance  of  Diseases  to  Offspring   145 

ents  and  upon  the  nature  of  the  crossing — must  depend, 
that  is  to  say,  upon  whether  the  parents'  bodies  contained 
diseased  germs  only  (as  certain  plants  in  the  experiments 
contained  red  germs  onW),  or  whether  the  parents'  bodies 
contained  germs  part  of  which  were  healthy  and  part  dis- 
eased (as  the  plants  of  the  first  crossed  generation  of  Men- 
del's experiments  contained  germs  with  red  and  white  rudi- 
ments). In  the  latter  case,  the  diseased  parents  are  them- 
selves the  offspring  of  diseased  ancestors,  and  of  such  a 
nature  are  most  of  the  cases  with  which  we  have  to  do. 
But  the  next  question  we  have  to  consider  is  whether  these 
diseased  individuals  unite  in  procreation  with  healthy  in- 
dividuals, or  with  others  who  are  similarly  abnormal. 

Let  us  first  consider  the  case  in  which  all  the  germinal 
cells  in  the  body  of  a  diseased  individual  are  themselves 
also  diseased.  This  occurs  in  those  parents  who  are  inde- 
pendently diseased,  and  also  in  the  case  of  25  per  cent,  of 
the  second  generation  (and  of  following  generations)  which 
have  resulted  from  the  conjugation  of  two  diseased  germi- 
nal cells  of  the  first  generation.  When  such  individuals 
procreate  in  conjunction  with  healthy  individuals  (or  in 
conjunction  with  those  similarly  affected  with  disease)  all 
the  offspring  must  be  diseased  if  the  pathological  state  is  a 
dominant  character.  On  the  whole  such  an  occurrence  is 
rare.  Neither  in  the  first  generation,  nor  in  genealogical 
trees  relating  to  several  generations,  do  we  often  find  that 
all  the  offspring  of  such  individuals  are  themselves  dis- 
eased. 

Secondly  let  us  suppose  that  we  have  to  do  with  dis- 
eased individuals  of  the  first  generation  (or  of  subsequent 
generations)  which  are  the  offspring  of  a  union  between  a 
diseased  person  and  a  healthy  onef,  and  in  whom  for  this 
reason  the  germinal  cells  are  partly  diseased  and  partly 
normal.  If  such  persons  procreate  in  conjunction  with 
healthy  individuals,  the  result  would  be  the  production  of 
offspring  one  half  of  whom  are  diseased.  Results  approxi- 
mating to  this  are  not  infrequently  observed  in  practice. 


146  Heredity,  Disease  and  Human  Evolution 

Thus,  in  the  cases  of  hypotrichosis  (deficiency  of  hair),  to 
which  reference  has  previously  been  made,  there  was  one 
family  in  which  there  were  three  diseased  children  and 
four  healthy,  and  another  in  which  seven  were  diseased 
and  seven  healthy.  Such  a  numerical  relationship  is  often 
more  plainly  manifest  when,  instead  of  considering  the 
separate  families,  we  deal,  as  in  the  experiments  upon 
plants,  with  all  the  children  of  all  the  families  of  each  gen- 
eration as  a  whole.  In  a  genealogical  tree  of  a  family 
affected  with  a  malformation  of  the  hand,  we  obtain,  for 
example,  in  four  successive  generations,  the  following  ratios 
between  healthy  and  diseased  members,  4  -A,  5 :7,  7  :9,  and 
17:16. 

Thirdly  and  finally,  when  diseased  individuals  whose  ger- 
minal cells  are  partly  healthy  and  partly  diseased  unite 
in  procreation  with  others  similarly  affected,  whether  these 
are  or  are  not  of  near  kin,  according  to  the  Mendelian 
rules  the  ratio  of  the  diseased  to  the  healthy  members  in 
the  second  generation  ought  to  be  3  :1.  A  clear  manifesta- 
tion of  such  a  numerical  relationship  is  seldom  encountered, 
and  objections  may  be  raised  against  many  genealogical 
trees  that  have  been  regarded  as  establishing  the  existence 
of  such  a  relationship.  It  is  true  that  the  genealogical 
trees  in  question  exhibit  the  required  numerical  ratios 
(three  diseased  children  to  one  healthy),  but  the  conditions 
affecting  the  parents  have  not  always  been  of  a  kind  that 
would  lead  us  to  expect  such  a  relationship.  When,  for 
example,  it  is  reported  that  of  the  two  parents  only  one  was 
diseased,  the  3 :1  ratio  ought  not  to  be  manifest.  If  the 
germs  in  the  body  of  the  diseased  parent  were  all  dis- 
eased, all  the  children  ought  to  be  diseased ;  while  if  the 
germs  in  the  body  of  the  diseased  parent  were  half  healthy 
and  half  diseased,  half  the  children  ought  to  be  diseased. 
"We  find,  then,  that  such  genealogical  trees  afford  but  inse- 
cure evidence.  Recently,  indeed,  F.  Pick  has  reported  a 
genealogical  tree  observed  by  Pribram  relating  to  diabetes, 
and  this  appears  to  comply  with  our  requirements.     Two 


Significance  of  Diseases  to  Offspring   147 

diseased  parents  had  four  children,  three  of  whom  were 
diseased  while  one  was  healthy.  We  know  nothing,  it  is 
true,  about  the  condition  of  the  germinal  cells  of  these  par- 
ents. In  the  following  generation,  however,  the  figures 
failed  to  correspond  to  the  Mendelian  canon.  One  of  the 
diseased  children,  married  to  a  healthy  individual,  had 
three  children,  two  of  whom  were  diseased  while  one  was 
healthy.  I  mention  these  observations  simply  for  the  rea- 
son that  I  am  about  to  explain  their  lack  of  precision. 

Hitherto  we  have  assumed  that  the  diseases  are  dominant, 
bearing  towards  health  the  relationship  that  the  red  col- 
ouration in  Mendel's  experiment  bore  towards  the  white, 
the  latter  character  being  termed  recesdve.  Every  charac- 
ter that  yields  before  another  is  recessive,  and  diseases  may 
do  this.  In  such  cases  they  may  appear  in  numerical  rela- 
tionships similar  to  those  exhibited  by  the  white-flowering 
plants  in  the  Mendelian  experiments.  Farabee  (quoted  by 
Haecker,  Allgemeine  Vererhungslehre,  1911)  observed  this 
in  a  case  of  albinism,  in  which  among  the  offspring  four 
individuals  were  aifected  with  albinism  and  eleven  free 
from  this  condition.  Here  also,  however,  the  figures  do  not 
precisely  correspond  to  the  requirements.  Pick,  again,  re- 
cords two  opposite  observations.  One  concerns  alcaptonu- 
ria,  a  disease  in  which  the  urine  exhibits  an  abnormally 
dark  colour  and  leaves  dark  stains  on  the  underlinen.  Of 
twelve  children,  three  were  affected  with  this  condition,  but 
no  definite  information  is  given  as  to  the  health  of  the 
parents.  The  other  case  relates  to  a  skin  disease,  the  so- 
called  xeroderma  pigmentosum.  Here  of  eleven  children 
three  were  affected.  The  parents,  however,  were  healthy, 
so  that  it  is  impossible  to  ascertain  what  would  have  been 
the  numerical  ratio  of  the  affected  children  to  the  immune. 
We  see  how  great  are  the  uncertainties  attending  the  dem- 
onstration of  Mendelian  inheritance  in  human  beings. 

Why  is  it  that,  in  the  inheritance  of  human  diseases,  we 
do  not  more  frequently  find  a  precise  correspondence  with 
Mendel's  figures,  although  segregation  of  characters  cer- 


/ 


148  Heredity,  Disease  and  Human  Evolution 

tainly  occurs — for  only  a  portion  of  the  offspring  is  af- 
fected with  hereditary  disease — while  we  are  forced  to  as- 
sume on  theoretical  grounds  that  the  process  of  disease-in- 
heritance must  take  the  same  course  as  that  which  we  ob- 
serve in  the  characters  of  plants  and  in  the  qualities  of 
normal  animals?  The  explanation  is  simple.  In  experi- 
ments upon  plants  nearly  all  the  ova  and  a  notable  pro- 
portion of  the  pollen  grains  engage  in  acts  of  mutual  fer- 
tilisation, and  out  of  these  large  quantities  good  average 
results  can  be  obtained.  In  the  case  of  human  procreation 
the  conditions  are  very  different.  The  number  of  the  off- 
spring is  often  so  inconsiderable  as  to  render  the  deduction 
of  general  rules  out  of  the  question.  Even  when  a  human 
pair  is  prolific,  when,  for  example,  the  offspring  number 
from  six  to  ten,  this  number  is  still  very  small  compared 
with  the  number  of  the  ova  that  actually  ripen  in  the 
human  female  during  the  period  of  reproductive  activity, 
for  this  number  is  about  360.  Really  valid  conclusions 
could  be  obtained  only  if  we  could  deal  with  this  total 
number,  and  to  gain  conclusions  even  approximately  valid 
we  should  need  to  deal  with  a  far  larger  number  of  in- 
stances than  ten.  We  therefore  could  not  expect  to  find 
Mendelian  rules  of  inheritance  applicable  on  the  average 
to  the  inheritance  of  human  diseases.  It  is  obviously  pos- 
sible that  in  isolated  instances  the  figures  may  correspond 
approximately  or  even  precisely  to  the  Mendelian  type,  as 
is  shown  by  the  cases  quoted  above.  It  is  impossible  to 
expect,  however,  that  we  shall  ever  be  in  a  position  to 
anticipate  the  exact  ratio  between  healthy  and  diseased) 
children. 

For  completeness  of  exposition  we  may  add  that  the  in- 
heritance of  normal  human  qualities  likewise  fails  to  corre- 
spond to  Mendelian  rules.  Undoubtedly  a  segregation  of 
characters  is  often  plainly  manifest.  A  permanent  admix- 
ture (analogous  to  that  whereby  in  the  experiments  on 
plants  the  admixture  of  white  and  red  produced  pink) 
is  exceptional.    Such  an  admixture,  indeed,  is  the  ordinary 


Significance  of  Diseases  to  Offspring   149 

outcome  of  intermarriage  between  negroes  and  whites,  for 
in  the  offspring  of  such  unions  we  observe  an  intermediate 
tint  of  skin,  which  persists,  when  mulattoes  interbreed,  in 
subsequent  generations.  Only  one  exception  to  this  rule 
has  hitherto  been  observed.  '  Certain  castaways  on  a  South 
Sea  island  intermarried  with  the  natives,  and  the  offspring 
of  the  first  generation  were  of  an  intermediate  colour.  In 
the  subsequent  generations,  however,  segregation  occurred, 
leading  to  the  production  of  distinctively  white  and  dis- 


Fig.  8. — Genealogical  Tree  showiixg  the  inheritance  of  curly  hair 
(after  Von  Gruber  and  Eiidin).  The  black  circles  denote  indi- 
viduals with  curly  hair.  The  figure  serves  to  demonstrate 
direct  inheritance  and  segregation. 

tinctively  coloured  individuals.  Apart  from  this  instance, 
we  have  no  information  as  to  the  segregation  of  racial 
characters.  In  the  case  of  other  normal  qualities,  how- 
ever, such  as  the  colour  of  the  eyes  and  the  hair,  segrega- 
tion is  often  observed.  In  one  family,  in  which  some  of 
the  members  had  straight  hair  and  others  curly  hair,  these 
two  characters  were  very  sharply  separated.  In  one  gen- 
eration there  were  eight  individuals  with  curly  hair  and 
eight  with  straight,  but  in  the  following  generation  the 
ratio  was  irregular,  for  there  were  six  individuals  with 
curly  hair  and  two  with  straight  (Gruber  and  Riidin,  Fort- 
pflanzung,  Vererbung,  Bassenhygiene,  1911).    AVe  see  that 


150  Heredity,  Disease  and  Human  Evolution 

here  the  inheritance  did  not  take  place  in  accordance  with 
definite  rules.  In  another  instance,  in  which,  as  a  family 
trait,  there  was  a  white  lock  in  the  midst  of  dark  hair,  some 
of  the  children  exhibited  this  peculiarity  and  others  did 
not,  but  here  also  the  numerical  ratios  were  irregular. 

It  appears,  then,  that  in  human  beings  the  rules  of  Men- 
delian  inheritance  are  as  little  applicable  to  normal  char- 
acters as  they  are  to  diseased  states,  but  in  view  of  what 
was  said  above  this  cannot  surprise  us.  Although  on  theo- 
retical grounds  we  should  expect  Mendelian  inheritance  to 
occur  in  human  beings,  it  is  impossible,  seeing  how  small  a 
proportion  of  the  human  germs  attain  to  fertilisation  and 
undergo  subsequent  development,  that  we  should  find,  in 
the  facts  of  human  inheritance,  an  approximate  corre- 
spondence with  Mendelian  rules. 

The  fact  remains  that  segregation  is  proved  to  occur  in 
human  beings  in  the  case  of  many  characters,  both  normal 
and  morbid.  This  is  a  matter  of  practical  as  well  as  of 
theoretical  importance,  as  will  be  shown  in  the  sequel. 

6.     Genesis  of  '* Hereditary"  Diseases 

The  genesis  of  hereditary  diseases  is  not  a  problem  of 
theoretical  interest  merely ;  it  is  also  one  of  great  practical 
importance.  Upon  its  solution  depends  the  answer  to  the 
further  questions,  whether  and  how  we  can  guard  against 
the  appearance  of  further  abnormal  states  in  addition  to 
those  that  already  exist,  and  whether  in  this  way  we  can 
acquire  a  controlling  influence  over  the  process  of  human 
evolution. 

In  our  previous  expositions  we  have  again  and  again 
contrasted  the  parental  bodies  and  the  germinal  cells,  and 
we  introduce  this  contrast  once  more  in  the  question  we 
have  now  to  ask,  which  runs  as  follows.  Where  do  the 
changes  originate  which  underlie  the  diseases  that  appear 
in  hereditary  forms ;  do  they  originate  in  the  bodies  of  the 
progenitors  or  in  their  germinal  cells?     To  one  who  first 


Significance  of  Diseases  to  Offspring   151 

approaches  this  problem  it  appears  self-evident  that  the 
pathological  change  must  originate  in  the  ancestral  body. 
If  something  must  be  transmitted  by  inheritance  from  par- 
ent to  offspring,  it  must  first,  it  would  seem,  exist  in  the 
parent.  This  reasoning,  however  unanswerable  it  may  seem 
at  first  sight,  does  not  apply  to  the  genesis  of  diseases,  for 
the  following  reasons.-  If  an  abnormal  state  is  to  appear 
in  the  offspring,  the  rudiment  of  the  abnormality  must 
already  exist  in  the  germ  out  of  which  the  new  individual 
is  to  proceed.  How  did  this  abnormality  find  its  way  into 
the  germ  ?  Did  it  originate  in  the  parental  organism,  to  be 
transferred  thence  to  the  germinal  cells  within  the  paren- 
tal body  ?  This  cannot  have  been  the  course  of  events,  for 
in  our  discussion  of  the  inheritance  of  acquired  characters 
(pp.  106  et  seq.)  we  saw  that  these  are  not  transmitted 
to  the  germinal  cells.  Even  if  some  persons  fail  to  recog- 
nise that  this  is  the  case  as  regards  normal  qualities,  no  one 
doubts  that  the  reasoning  applies  to  morbid  states.  It  is 
impossible  for  the  disease-producing  changes  in  the  organs 
to  be  transferred  as  such  in  an  equivalent  sense  to  the 
germs.  The  reasons  for  this  impossibility  have  already 
been  studied,  but  it  is  necessary,  in  the  present  connexion, 
to  return  to  the  matter. 

How  does  the  pathological  change  whose  recurrence  we 
observe  in  the  offspring  originate  in  the  body  of  the  pro- 
genitor ?  It  originates  in  this  way,  that  some  noxious  influ- 
ence affects  the  tissues  and  injures  them,  the  disease  being 
dependent  upon  this  injury.  To  explain  the  recurrence 
of  the  disease  in  the  offspring  we  should  be  forced  to 
assume  that  this  change  has  exerted  an  influence  upon  the 
germ,  for  only  in  this  way  could  a  corresponding  patho- 
logical transformation  be  effected  in  the  germ.  But  if  this 
happens,  the  change  that  has  taken  place  in  the  parental 
body  must  effect  in  the  germ  the  same  transformation  which 
the  external  noxious  influence  has  affected  in  the  parental 
body.  Let  us  assume,  for  example,  that  the  noxious  influ- 
ence has  induced  a  malformation  in  one  of  the  parental 


152  Heredity,  Disease  and  Human  Evolution 

organs,  this  malformation  must  in  its  turn  so  affect  the  germ 
as  to  induce  in  the  corresponding  organic  rudiment  in  the 
germ  the  potentiality  of  the  like  malformation.  But  this 
is  impossible,  for  to  assume  that  it  is  possible  involves  the 
belief  that  the  like  abnormality  may  be  induced  by  two 
entirely  different  causes,  in  the  parental  body  by  the 
noxious  influence  from  without,  and  in  the  germ  by  the  in- 
fluences that  proceed  from  the  altered  parts.  To  give  an- 
other example,  on  this  reasoning  we  should  be  forced  to 
believe  that  a  valvular  defect  of  the  heart  caused  by  micro- 
organisms must  be  potentially  produced  in  the  germ  by  the 
disturbances  of  circulation  in  the  parent  that  are  the  out- 
come of  the  valvular  defect.  This  course  of  events  is  obvi- 
ously inconceivable. 

It  follows  that  the  primary  genesis  of  a  hereditary  dis- 
ease cannot  take  place  in  the  parental  body,  but  only  in  the 
germ.  Once  this  latter  has  been  altered,  the  transmission 
of  the  change  to  subsequent  generations  will  obviously 
occur  in  accordance  with  the  principles  explained  in  an 
earlier  section  (p.  102). 

How  does  the  germ  undergo  alteration  ?  Is  not  the  proc- 
ess related  in  some  way  to  the  existence  of  disease  in  the 
parental  body?  This  is  undoubtedly  the  case.  Almost 
without  exception,  disturbances  in  the  structure  of  the 
germ  are  due  to  changes  in  the  parental  body.  It  is  doubt- 
less conceivable  that  a  blow  or  a  squeeze  might  so  affect 
the  reproductive  gland  as  to  injure  the  germinal  cells  it 
contains  without  any  suffering  on  the  part  of  the  rest  of 
the  parental  organism.  But,  to  say  the  least  of  it,  such  an 
occurrence  must  be  rare. 

Is  there  not,  it  may  be  asked,  a  contradiction  involved, 
if  we  say,  on  the  one  hand,  that  acquired  diseases  are  not 
transmitted  to  the  germs,  and,  on  the  other,  that  ova  and 
spermatozoa  can  become  diseased  only  through  the  inter- 
mediation of  the  parental  body?  The  contradiction  is  ap- 
parent merely.  The  change  in  the  germs  that  arises 
through  the  intermediation  of  the  parental  body  does  not 


Significance  of  Diseases  to  Offspring   153 

arise  because  an  abnormal  condition  previously  affecting 
the  parent  now  per  sc  influences  the  germ,  but  in  another 
way.  First  of  all,  it  may  be  that  the  pathological  changes 
in  the  parental  organism  injure  the  germinal  cells  in  one 
way  or  another,  but  they  never  do  so  in  such  a  way  as  to 
evoke  in  the  germ  the  identical  condition  that  exists  in  the 
parent.  Secondly,  the  noxious  influence  that  affects  the 
parental  organism  may  not  limit  its  action  to  that  organ- 
ism, but  may  also  exert  an  injurious  effect  upon  the  germ. 
In  either  case,  the  morbid  disposition  is  independently  pro- 
duced in  the  germ. 

Some  examples  will  make  this  clear.  To  consider  the 
first  mode  of  action,  let  us  suppose  that  in  the  parent  there 
occurs  an  inflammation  of  the  kidneys,  induced  by  micro- 
organisms or  by  poisons,  and  that  the  outcome  of  the  dis- 
ease is  that  substances  which  should  be  eliminated  by  the 
kidneys  are  now  retained  within  the  body  and  act  as 
poisons.  The  germ  may  also  suffer  from  the  action  of  these 
poisons,  but  it  does  not  necessarily  follow  that  what  is  in- 
jured in  the  germ  will  be  the  rudiment  of  the  kidneys  so 
that  in  the  child  that  subsequently  develops  there  will  also 
'be  changes  in  these  organs.  It  is  more  probable  that  if 
the  retained  substances  affect  the  germ  at  all,  the  rudi- 
ments injured  will  be  those  of  the  same  parts  that  are 
injuriously  affected  hy  these  substances  in  the  parent,  that 
is  to  say  the  heart  and  the  brain.  Thus  the  child  of  the 
parent  suffering  from  kidney  disease  might  suffer  from 
some  impairment  of  the  mental  functions. 

It  is  doubtless  conceivable  that  the  poisons  in  question 
might  attack  the  kidney-rudiment  of  the  germ.  First,  how- 
ever, we  may  be  certain  that  the  result  would  not  be  to 
induce  a  kidney  disease  of  the  same  kind  as  that  which  has 
been  caused  in  the  parent  in  another  way,  by  quite  differ- 
ent poisons;  and  secondly  we  should  have  to  do  here,  not 
with  the  transference  of  an  organic  change  to  the  germ,  but 
merely  with  the  independent  production  of  a  disturbance 
in  the  kidney  rudiment  of  the  germ. 


154  Heredity,  Disease  and  Human  Evolution 

Let  us  take  another  example.  When  in  the  parental 
body  the  thyroid  undergoes  changes  leading  to  the  produc- 
tion of  Graves'  disease,  the  chief  incidence  of  this  affection 
is  upon  the  nervous  system,  for  there  ensues  a  marked  gen- 
eral nervousness  in  conjunction  with  other  disorders.  If 
we  accept  the  view  that  the  symptoms  of  the  disease  arise 
in  consequence  of  the  production  of  abnormal  substances 
by  the  thyroid,  substances  which  act  as  poisons  in  the 
parental  body,  it  is  obvious  that  the  germ  may  also  be 
injuriously  affected  by  these  poisons.  On  what,  however, 
would  the  poisons  take  effect.  Naturally  upon  the  nervous 
system,  or  rather  upon  the  rudiment  of  that  system,  and 
it  would  be  theoretically  conceivable  (although  we  have 
no  evidence  that  anything  of  the  kind  occurs)  that  the 
individual  subsequently  developed  out  of  the  germ  thus 
injured  might  display  like  nervous  disturbances.  On  the 
other  hand,  it  is  not  possible  that  the  rudiment  of  the 
thyroid  in  the  germinal  cell  should  be  affected  in  the  same 
way  as  the  thyroid  is  affected  in  the  parent,  that  the  thy- 
roid-rudiment should  undergo  such  a  change  as  to  induce 
subsequently  the  appearance  of  Graves'  disease  in  the  off- 
spring. In  the  parent  the  changes  in  the  thyroid  are  caused 
in  an  altogether  different  way,  and  in  that  way  only  could 
a  corresponding  change  be  induced  in  the  thyroid-rudiment 
of  the  germ. 

As  regards  the  second  kind  of  causation,  that  in  which 
the  germs  are  directly  injured  by  noxious  influences  that 
affect  the  parental  body,  we  may  illustrate  the  mode  of 
operation  by  reference  to  the  diseases  caused  by  micro- 
organisms. When  such  organisms  give  rise  to  an  inflamma- 
tion of  the  valves  of  the  heart,  this  inflammation  is  not 
transmitted  as  such  to  the  germ.  It  is  possible  that  the 
toxins  produced  by  the  micro-organisms  may  injure  the 
heart-rudiment  of  the  germ.  It  may  then  result  that  the 
child  will  have  an  abnormal  heart,  perhaps  one  of  the 
familiar  congenital  malformations  of  that  organ,  but  it  will 
certainly  not  have  an  inflammation  of  the  cardiac  valves. 


Significance  of  Diseases  to  Offspring  155 

for  such  inflammation  is  not  induced  by  toxins  but  by  the 
direct  action  of  micro-organisms.  If  it  be  suggested  that 
the  organisms  themselves  might  invade  the  germ,  it  suf- 
fices to  answer  that  they  can  exercise  an  inflammatory  in- 
fluence upon  the  valves  only  vv^hen  these  actually  exist. 
Since,  however,  in  the  germ  there  are  no  heart-valves,  but 
only  the  rudiments  of  these,  it  is  impossible  for  the  micro- 
organisms to  act  in  the  suggested  way.  It  is,  in  fact,  highly 
improbable  that  these  particular  organisms  invade  the 
germs  at  all,  and  failing  such  direct  invasion  they  can  act 
on  the  germs  only  through  their  toxins.  If  they  do  this, 
it  does  not  follow  that  the  heart-rudiment  will  be  the  one 
affected,  for  their  injurious  influence  may  be  exerted  upon 
some  other  rudiment.  Similar  considerations  apply  to  all 
the  other  infectious  diseases.  These  involve  dangers,  not 
only  to  the  parental  organism,  but  also  to  the  germinal  cells 
(and  in  many  eases  it  is  the  brain-rudiment  which  is  espe- 
cially exposed  to  danger).  It  does  not  follow  that  the 
injurious  influence  will  be  exercised  upon  the  same  organ 
both  in  parent  and  in  germ.  Even  if  this  should  be  the 
case,  what  has  occurred  is  not  a  transference  of  the  change 
from  the  parental  organ  to  the  rudiment  of  that  organ  in 
the  germ,  but  merely  an  independent  production  of  the 
change  in  the  germ. 

The  non-bacterial  poisonings  furnish  us  with  an  addi- 
tional example,  and  the  most  salient  of  these  is  alcoholic 
poisoning.  Alcohol  permeates  the  parental  body,  and  be- 
sides affecting  one  or  other  organ  in  this  body,  such  as  the 
liver  or  the  brain,  it  may  injure  the  rudiments  of  these 
organs  in  the  germ.  In  such  a  case  the  offspring  will  ex- 
hibit morbid  phenomena  similar  to  those  manifested  by  the 
parents.  Here  like  changes  are  independently  induced  in 
two  different  places,  but  there  has  been  no  transference; 
of  the  brain  anomaly,  for  instance,  from  the  parent  to  the 
germ. 

These  examples  may  suffice.  They  show  clearly  that  the 
germinal  cells  may  be  injured  in  consequence  of  abnormal 


156  Heredity,  Disease  and  Human  Evolution 

conditions  in  the  parental  body,  but  that  in  such  cases  we 
never  have  to  do  with  the  transference  to  the  germs  of 
morbid  conditions  acquired  by  the  parents.  It  has  been 
shown,  on  the  contrary,  that  morbid  states  in  the  germ 
arise  always  independently  of  those  in  the  parent,  and  that 
the  former  states  are  sometimes  induced  by  a  similar  proc- 
ess of  causation  as  the  latter,  and  sometimes  in  a  different 
way. 

The  inheritable  diseases  that  appear  in  the  following  gen- 
eration therefore  originate  in  the  germ,  not  in  the  parent, 
although  the  abnormal  state  of  the  body  of  the  parent  is 
an  intermediary  factor  in  the  production  of  the  independ- 
ently arising  lesion  of  the  germ. 

Let  us  now  pass  from  these  theoretical  considerations  to 
examine  what  we  actually  know  as  to  the  genesis  of  hered- 
itary diseases.  These  must  be  divided  into  two  categories, 
requiring  separate  consideration. 

In  the  first  category  we  place  numerous  hereditary  patho- 
logical states  about  whose  genesis  as  diseases  of  the  germ 
we  know  absolutely  nothing.  To  this  class  belong  haemo- 
philia, colour-blindness,  night-blindness,  various  malforma- 
tions, many  anomalies  of  the  skin  and  of  the  eye,  polyuria, 
alcaptonuria,  tumours,  obesity,  gout,  diabetes,  and  many 
changes  of  the  nervous  system. 

What  ideas  can  we  form  as  to  the  genesis  of  these  dis- 
eases ? 

The  first  possibility  is  that  some  pathological  condition 
in  the  parent  has  exercised  an  injurious  influence  upon  the 
germ.  There  may  have  been  a  kidney  change,  an  anomaly 
of  the  thyroid,  some  infectious  disease  in  consequence  of 
which  bacterial  toxins  have  been  at  work,  diabetes,  etc.,  and 
the  consequence  may  have  been  that  one  or  other  germinal 
rudiment  has  been  injured,  the  one  to  be  affected  being  de- 
pendent upon  the  nature  of  the  injurious  influence  arising 
out  of  parental  disease.  It  is  conceivable  that  toxins  might 
give  rise  to  disturbances  in  the  rudiment  of  the  eye  or  in 
that  of  the  skin,  that  haemophilia  might  be  induced  by 


Significance  of  Diseases  to  Offspring   157 

some  influence  affecting  the  vascular  rudiment,  that  mal- 
formations might  be  the  outcome  of  changes  operating  on 
the  rudiments  of  individual  organs  or  extremities,  or  that 
hereditary  mental  disorder  might  be  caused  by  injury  to 
the  brain-rudiment.  But  we  lack  well-grounded  observa- 
tions in  support  of  any  such  hypothesis,  nor  can  we  con- 
ceive how  such  observations  are  to  be  made.  It  is  impos- 
sible for  us  directly  to  observe  an  injury  to  the  germ. 
Only  by  way  of  an  extraordinarily  laborious  statistical  in- 
vestigation could  we  attain  to  any  result,  namely  by  making 
a  detailed  examination  of  the  family  histories  of  those  af- 
fected with  certain  anomalies,  and  drawing  conclusions 
from  the  frequency  of  coincident  phenomena.  But  such  a 
method  will  always  remain  extremely  uncertain. 

A  second  conceivable  possibility  is  that  the  germs  de- 
rived from  the  respective  parents  are  unsuitable  to  one 
another,  and  that  this  unsuitability  leads  to  disturbances 
in  the  act  of  fertilisation.  This  is  a  possibility  which  has 
often  been  mooted,  but  the  attainment  of  secure  principles 
is  here  hardly  possible.  It  is  merely  a  hypothetical  ex- 
planation, proposed  in  the'  lack  of  something  better. 

In  the  third  place  it  is  necessary  to  point  out  that  the 
origination  of  diseases  de  novo  may  well  be  apparent 
merely.  There  is  no  doubt  that  germinal  anomalies  may 
remain  latent  for  generations,  and  only  manifest  themselves 
again  when  circumstances  arise  specially  favourable  to  their 
appearance.  If  the  former  occurrence  of  these  pathologi- 
cal states  has  been  forgotten,  they  are  supposed  to  have 
originated  de  novo.  There  can  be  no  doubt  that  such  obliv- 
ion plays  a  large  part  in  the  explanation.  We  are  led 
to  see  this  by  the  simple  consideration  that  none  of  the 
morbid  states  to-day  observed  to  be  hereditary  made  their 
first  appearance  in  the  times  in  which  we  now  live.  It  is 
practically  certain  that  they  have  always  existed.  If,  how- 
ever, this  is  so,  they  may  from  time  to  time  have  become 
latent,  and  have  subsequently  reappeared.  When  we  exam- 
ine genealogical  trees  that  cover  a  sufficient  number  of 


158  Heredity,  Disease  and  Human  Evolution 

generations,  we  can  actually  verify  this  fact.  The  diseases 
disappear  from  time  to  time,  it  may  be  for  two  or  three 
generations.  As  a  rule  such  a  period  of  latency  suffices 
to  make  people  forget  the  earlier  occurrence  of  the  dis- 
ease— at  any  rate  until  it  reappears.  And  the  period  of 
latency  may  exceed  two  or  three  generations. 

The  objection  may  be  made  that  such  a  view  affords  no 
aid  in  explaining  the  genesis  of  disease.  This  is  perfectly 
true.  The  further  back  into  the  ancestry  we  traced  the 
incidence  of  a  disease,  the  less  do  we  secure  any  useful 
lights  as  to  its  etiology.  Ultimately  we  find  that  there  is 
hardly  any  other  conclusion  open  than  to  regard  such  dis- 
eases as  anomalies  permanently  affecting  the  human  race, 
making  their  appearance  from  time  to  time  after  longer 
or  shorter  intervals  of  latency.  At  first  sight  this  view 
may  seem  astonishing,  but  we  must  bear  in  mind  the  pos- 
sibility that  many  hereditary  anomalies  may  find  their  ulti- 
mate explanation  in  the  persistence  in  human  beings  of  cer- 
tain peculiarities  derived  from  our  pre-human  ancestors, 
characteristics  which  are  not  now  properly  adapted  to  the 
human  organisation,  and  are  therefore  in  our  own  day  no 
more  than  intrusive  abnormalities.  We  think,  in  this  con- 
nexion, of  some  of  the  anomalies  of  the  skin,  of  certain  mal- 
formations, of  colour-blindness.  Such  considerations  as 
these,  which  are  of  necessity  purely  speculative,  must  not 
be  carried  too  far.  We  may,  however,  refer,  in  passing,  to 
the  well-known  fact  that  Lombroso  has  endeavoured  to  ex- 
plain criminal  tendencies  as  a  reversion  to  the  savagery  of 
the  ancestors  of  our  race. 

Some  brief  remarks  upon  atavism  will  here  be  appropri- 
ate. If  the  objection  be  made  that  we  are  hardly  justified 
in  assuming  a  reversion  to  characters  belonging  to  so  re- 
mote an  epoch,  the  soundness  of  this  contention  might  be 
admitted  if  what  was  supposed  to  occur  were  the  reap- 
pearance of  a  character  which  had  been  in  complete  abey- 
ance throughout  the  intervening  period.  But  such  an 
assumption  is  unnecessary.    We  may  suppose  fhat  the  ab- 


Significance  of  Diseases  to  Offspring  159 

normality  may  have  recurred  at  intervals  since  prehis- 
toric days.  In  that  ease  we  should  really  have  to  do,  not 
with  true  atavism,  but  with  discontinuous  inheritance,  a 
condition  which  offers  no  difficulties  to  our  understanding, 
and  one  whose  existence  we  are  justified  in  postulating  as 
the  real  explanation  of  the  phenomenon  known  as  atavism 
— the  recurrence  of  ancestral  characters,  not  merely  in 
our  own  time,  but  at  intervals  throughout  the  history  of 
our  race.  These  remarks  naturally  apply,  not  only  to  mor- 
bid characters,  but  to  all  those  characters  in  explanation  of 
which  the  idea  of  atavism  has  been  invoked. 

There  is  an  additional  consideration  that  may  be  adduced 
in  support  of  the  derivation  of  hereditary  diseases  from 
remote  generations  of  our  ancestry.  It  is  one  brought  to 
light  by  the  application  of  Mendelian  principles  to  the 
study  of  morbid  inheritance. 

If  in  any  family  one  of  the  diseases  whose  genesis  re- 
mains unexplained  appears  (apparently)  de  novo,  we  never 
observ^e  that  all  the  offspring  are  affected.  Some  invariably 
remain  exempt.  To  express  the  matter  otherwise,  this  sig- 
nifies that  the  germinal  cells  from  which  the  children  pro- 
ceed had  not  all  undergone  alteration.  This  partial  ex- 
emption would,  however,  be  inexplicable  if  the  germinal 
cells  had  been  affected  by  injurious  influences  operating 
within  the  parental  body.  For  in  such  a  case  we  are  com- 
pelled to  believe  that  all  would  suffer  alike.  It  is,  indeed, 
conceivable,  as  previously  explained  (p.  137),  that  the 
injurious  influence  did  not  begin  to  operate  until  after  the 
birth  of  some  of  the  children,  and  that  for  this  reason  the 
later  children  only  were  affected.  But  such  a  distribution 
of  disease  in  a  family  is  not  commonly  observed.  What  we 
usually  see  is  an  irregular  distribution  among  the  offspring. 
It  follows  that  from  the  first  only  a  portion  of  the  germs 
can  have  been  diseased,  and  in  that  case  it  is  impossible 
that  the  pathological  condition  can  have  come  into  existence 
within  the  parental  organism.  It  must  derive  from  earlier 
generations.    At  that  time,  a  germ  diseased  for  some  rea- 


160  Heredity,  Disease  and  Human  Evolution 

son  united  with  a  healthy  one,  and  subsequently  the  Men- 
delian  process  of  segregation  ensued,  in  consequence  of 
which,  in  subsequent  generations,  there  always  existed  in 
the  individual  body  both  healthy  and  diseased  germs  (as 
in  the  Mendelian  experiments  on  plants  there  existed  red 
and  white  ova)  in  approximately  equal  numbers.  In  that 
case  it  is  obvious  that  only  a  portion  of  the  offspring  would 
become  ill,  and  in  accordance  with  Mendel's  rules  about  one 
half  of  them  would  be  diseased.  Since  this  is  what  we 
actually  observe,  we  must  conclude  that  the  disease  which 
apparently  originates  de  novo  really  derives  from  an  earlier 
stage  in  ancestral  history  than  that  occupied  by  the  appar- 
ently healthy  parents. 

Yet  another  attempt  has  been  made  to  explain  the  gene- 
sis of  hereditary  morbid  conditions.  It  has  been  suggested 
that  these  anomalies  may  appear  as  mutations  (sports)  in 
the  human  evolutionary  process,  that  is  to  say,  as  discon- 
tinuous variations,  of  the  same  character  as  those  shown 
by  de  Vries  to  occur  in  plants,  and  since  then  largely 
utilised  in  the  theory  of  evolution.  Mutations,  however, 
are  perfectly  normal  phenomena,  which  play  their  part  in 
the  general  process  of  evolution  of  the  entire  organic  world, 
and  which  manifest  themselves  within  this  process  without 
the  operation  of  any  special  causative  factors.  It  is  impos- 
sible to  regard  abnormal  conditions  as  upon  the  same  foot- 
ing with  these.  It  is  inconceivable  that  the  typical  develop- 
ment of  organisms  could  ever  of  itself  give  rise  to  morbid 
variations.  To  suppose  this  would  be  in  complete  con- 
tradiction with  the  concept  of  mutation.  It  is  therefore 
impossible  to  accept  the  suggested  explanation,  and  to 
admit  that  the  occurrence  of  haemophilia  or  of  colour- 
blindness can  be  explained  as  a  process  of  mutation.  If, 
further,  it  be  suggested  that  we  may  assume  some  new 
influence  to  have  induced  the  changes,  this  idea  also  is  out 
of  harmony  with  the  concept  of  mutation.  All  that  we 
should  have  in  such  a  ease  would  be  the  production  of  dis- 


Significance  of  Diseases  to  Offspring  161 

ease  by  noxious  influences.  Hence  it  is  impossible  to  invoke 
mutation  to  explain  the  genesis  of  morbid  states. 

The  second  category  of  hereditary  diseases  comprises 
those  as  to  whose  genesis  we  believe  ourselves  to  possess 
more  or  less  valid  explanations.  The  first  place  in  this 
group  is  occupied  by  nervous  and  mental  disorders  (epi- 
lepsy, idiocy,  imbecility,  and  the  various  diseases  of  the 
mind).  According  to  the  views  now  dominant,  these  dis- 
eases arise  through  a  poisoning  of  the  germinal  cells,  in 
many  cases  effected  by  the  toxic  products  of  various  micro- 
organisms. It  is  true  that  in  this  connexion  indisputable 
facts  are  lacking,  but  those  who  support  the  theory  lay 
especial  stress  upon  the  case  of  syphilis.  With  good  reason 
we  ascribe  to  the  toxins  manufactured  by  the  organisms 
that  are  the  exciting  causes  of  this  disease  an  exceptionally 
powerful  influence  upon  the  nervous  system.  "We  know 
that  locomotor  ataxia  and  general  paralysis  of  the  insane 
must  be  regarded  as  sequels  of  syphilitic  infection.  It  is, 
therefore,  readily  comprehensible,  and  indeed  probable, 
that  the  same  toxins  may  affect  the  rudiments  of  the  nerv- 
ous system  in  the  germinal  cells. 

Among  the  non-bacterial  toxins  alcohol  is  especially 
blamed  for  the  appearance  of  numerous  mental  disorders 
which  are  supposed  to  be  caused  by  the  influence  of  this 
poison  upon  the  germinal  cells.  No  doubt  this  accusation 
is  justified.  "We  see,  on  the  one  hand,  that  alcohol  exerts 
its  influence  above  all  on  the  central  nervous  system,  and 
that  alcoholics  frequently  suffer  from  mental  disorder.  On 
the  other  hand  we  know  that  the  whole  body  of  the  drinker 
is  permeated  with  the  poison,  so  that  the  germinal  cells  as 
well  as  others  may  be  injured  thereby.  Thus  it  is  possible 
that  in  this  action  on  the  germinal  cells  rudiments  of  the 
central  nervous  system  may  be  injured  in  such  a  way  that 
the  individuals  subsequently  developed  exhibit  mental 
anomalies. 

In  view  of  the  great  importance  ascribed  to  alcohol  we 
shall  discuss  its  influence  in  fuller  detail 


162  Heredity,  Disease  and  Human  Evolution 

As  regards  the  demonstrable  anatomical  influence  of  al- 
cohol upon  the  reproductive  glands,  recent  researches  seem 
to  show  that  this  influence  is  exerted  upon  the  spermatozoa- 
producing  cells  of  the  testicle.  In  a  large  percentage  of 
drinkers  it  has  been  possible  to  demonstrate  the  occurrence 
of  destruction  of  the  seminiferous  tubules  and  their  re- 
placement by  connective  tissue.  But  before  the  germinal 
cells  are  completely  destroyed  they  will  naturally  be  in- 
jured in  some  way.  If  at  this  stage  in  the  process,  and 
before  the  alteration  is  too  extensive,  spermatozoa  are  pro- 
duced and  take  part  in  fertilisation,  the  injury  they  have 
suffered  may  have  harmful  results  in  the  newly-formed  in- 
dividuals. Forel,  who  has  devoted  himself  to  a  thorough 
study  of  the  consequences  of  alcoholic  intoxication,  gives 
to  this  process  of  poisoning  of  the  germ  the  name  of  hlas- 
taphthoria. 

Among  the  consequences  ascribed  to  the  effect  of  alcohol 
upon  the  germinal  cells  is  one  suggested  by  von  Bunge, 
who  believes  the  incapacity  of  the  daughters  of  drunkards 
to  suckle  their  children  to  be  due  to  this  cause.  He  re- 
garded as  especially  significant,  cases  in  which  mothers,  the 
wives  of  drinkers,  could  suckle  their  children,  while  their 
daughters  were  unable  to  do  so.  This  incapacity  of  the 
daughters  of  alcoholics  to  suckle  their  children  is  said  to 
be  transmitted  to  subsequent  generations.  Several  addi- 
tional investigators  have  confirmed  von  Bunge 's  statistical 
statements ;  but  others,  and  especially  Agnes  Bluhm  regard 
his  conclusions  as  unsound.  Above  all,  it  has  to  be  ad- 
mitted that  the  reports  as  to  the  amount  of  alcohol  con- 
sumed by  the  father  are  not  always  sufficiently  precise,  and 
also  that  the  failure  of  the  daughter  to  suckle  her  child 
may  sometimes  be  the  outcome,  not  of  inability,  but  of  un- 
willingness. In  the  case  of  39  of  the  daughters  of  alco- 
holics, A.  Bluhm  found  25  fully  competent  to  suckle  (64 
per  cent.),  and  among  the  remaining  14  not  all  were  com- 
pletely incompetent.    At  present  we  still  lack  further  light 


Significance  of  Diseases  to  Offspring  163 

on  these  contradictory  results,  and  the  question  must  there- 
fore remain  open. 

A.  Bluhm  has  approached  the  problem  more  directly  by 
experiments  on  animals.  She  administered  poisonous  doses 
of  alcohol  to  male  rats  during  many  months,  but  was  un- 
able to  observe  any  diminution  in  the  capacity  for  suckling 
on  the  part  of  the  female  offspring  of  these  animals. 

The  possibility  of  other  consequences  of  alcoholic  poison- 
ing has  been  made  the  subject  of  experiment.  Ethylic  al- 
cohol was  administered  to  fowls  for  a  number  of  years.  It 
resulted  that  in  the  eggs  of  these  birds  the  chickens  devel- 
oped imperfectly,  suggesting  that  the  germs  had  been 
injured  by  the  alcohol.  It  might  be  objected  that  the 
health  of  the  parent  birds  had  been  depressed  by  the  alco- 
holic poisoning,  that  for  this  reason  they  produced  defec- 
tive eggs,  so  that  the  imperfect  development  was  not  the 
direct  effect  of  the  alcohol.  Still,  the  experiments  were 
not  without  value,  for  even  if  there  did  not  occur  a  genu- 
ine intoxication  of  the  germinal  cells,  nevertheless  the 
germs  had  been  indirectly  injured,  and  for  this  reason  in- 
dividuals may  have  been  born  with  transmissible  defects. 
Thus  the  alcoholic  intoxication  had  a  causative  influence. 

In  another  series  of  experiments,  dogs  were  given  beer. 
The  offspring  of  these  animals  drank  beer  in  preference  to 
water.  It  was  inferred  from  this  that  the  germs  had  been 
injured  by  alcohol  in  such  a  way  as  to  give  rise  to  the 
abnormal  habit  in  the  offspring.  To  this  the  objection  has 
been  raised  that  the  suckling  mother-animals  were  still 
being  given  beer,  and  that  the  bitter  substances  in  this  bev- 
erage are  excreted  in  the  milk.  The  puppies  might  well 
have  become  so  habituated  to  this  bitter  flavor  that  when, 
after  suckling  had  been  discontinued,  they  wanted  to 
quench  their  thirst,  the  bitter-tasting  beer  would  be  more 
agreeable  to  them  than  water.  It  is  therefore  not  necessary 
to  assume  that  the  craving  for  alcohol  was  itself  trans- 
mitted by  inheritance. 

Certain  other  experiments  are  on  record  in  which  alco- 


164  Heredity,  Disease  and  Human  Evolution 

hoi  was  administered  to  dogs  for  years,  and  in  which  the 
offspring  of  these  animals  showed  an  exceptionally  high 
and  early  mortality,  or  were  epileptic,  atrophied,  or  mal- 
formed. We  can  hardly  avoid  the  conclusion  that  these 
anomalies  were  dependent  upon  intoxication  of  the  germ. 

Experiments  upon  guinea  pigs  made  hy  Laitinen  showed 
that  the  offspring  of  animals  poisoned  with  alcohol  devel- 
oped imperfectly  as  compared  with  the  animals  in  control 
experiments,  and  that  the  former  were  less  resistant  to 
infectious  diseases  than  the  latter. 

A  like  result  has  heen  estahlished  in  other  experiments. 
Kern  intoxicated  animals  with  daily  doses  of  alcohol  and 
then  infected  them  with  tubercle  bacilli.  The  alcoholised 
animals  died  more  quickly  and  in  a  larger  percentage  than 
animals  in  control  experiments.  Laitinen  obtained  similar 
results.  He  infected  rabbits  and  guinea  pigs  with  tubercle 
bacilli,  and  to  some  of  the  animals  gave  alcohol  in  addition 
to  their  food,  but  to  others  water  only.  The  alcoholised 
animals  died  in  larger  percentage.  He  found,  in  addition, 
that  the  offspring  of  the  alcoholised  animals  died  in  a 
much  greater  proportion.  The  reason  for  the  difference  is 
probably  to  be  found  in  the  fact  that  alcohol  inhibited  the 
formation  of  antitoxins  in  the  body,  and  that  this  disturb- 
ance was  transmitted  to  the  offspring  through  the  inter- 
mediation of  the  poisoned  germinal  cells. 

We  have  no  reason  to  suppose  that  what  has  been  estab- 
lished by  such  experiments  upon  animals  is  inapplicable  to 
human  beings.  Moreover,  the  accuracy  of  these  theoretical 
deductions  is  confirmed  by  experience.  There  is  abundant 
evidence  to  show  that  the  children  of  drunkards  exhibit  an 
excessively  high  and  early  mortality.  According  to  statis- 
tical data  collected  by  Sichel,  among  523  such  children, 
only  203  were  known  to  be  healthy,  as  to  118  precise  infor- 
mation was  lacking,  200  died  before  or  shortly  after  birth. 
Of  these  last,  51  were  born  prematurely,  20  stillborn,  75 
died  almost  immediately  after  birth,  21  succumbed  to  con- 
vulsions, and  32  to  infectious  diseases — the  death  of  these 


Significance  of  Diseases  to  Offspring  165 

last  illustrating  the  before-mentioned  lack  of  resisting 
power  to  infectious  diseases  exhibited  by  the  offspring  of 
drunkards. 

If  we  are  justified  in  concluding  from  such  observations 
that  alcoholism  in  the  parent  diminishes  vital  capacity  in 
the  children,  we  must  also  recognise  that  in  those  children 
of  alcoholics  who  survive,  the  poison  may  induce  all  kinds 
of  injuries  in  various  organs,  and  above  all  in  the  brain. 

Alienists  are  in  general  agreed  that  alcoholism  plays  a 
great  part  in  the  causation  of  mental  disorders,  and  the 
only  difference  of  opinion  is  as  to  the  extent  of  its  influ- 
ence. 

In  the  family  histories  of  those  admitted  to  lunatic  asy- 
lums the  excessive  use  of  alcohol  is  a  common  feature,  and 
in  many  statistical  statements  the  percentage  of  lunatics 
who  have  had  alcoholics  among  their  progenitors  is  so  high 
that  we  cannot  doubt  the  existence  of  a  causal  connexion. 

The  offspring  of  drinkers  are  in  many  cases  drinkers 
themselves,  and  they  may  suffer,  either  independently  or 
in  association,  from  a  tendency  to  alcoholism,  from  various 
forms  of  mental  disorder,  and  especially  from  epilepsy  and 
from  dementia  praecox. 

Alcohol  plays  a  very  great  part  in  the  causation  of  epi- 
lepsy. In  one  series  of  cases,  in  which  particulars  were 
collected  relating  to  83  epileptic  girls,  in  60  of  them  it  could 
be  shown  that  alcoholism  existed  in  the  parents. 

In  the  case  of  school  children  exhibiting  deficient  intel- 
ligence, alcoholism  in  the  parents  can  be  shown  to  exist 
in  a  high  percentage  of  cases.  In  a  recent  report  on  this 
subject  by  Schlesinger,  drunkenness  in  the  parents  was 
proved  to  exist  in  30  per  cent,  of  such  children.  This  num- 
ber, however,  is  certainly'  below  the  mark.  AVhen  the 
children  with  deficient  intelligence  from  the  families  of 
alcoholics  were  compared  Avith  those  of  the  children  with 
deficient  intelligence  from  sober  families,  the  former  con- 
trasted very  unfavourably  in  development  with  the  latter. 


166  Heredity,  Disease  and  Human  Evolution 

Defects  of  intelligence  and  of  character  were  far  more  con- 
spicuous in  those  with  an  alcoholic  family  history. 

In  contrast  with  these  and  similar  experiences,  the  re- 
ports of  Pearson  and  Elderton  have  attracted  great  at- 
tention. They  give  the  results,  among  others,  of  investiga- 
tions relating  to  1,450  school  children  from  among  the 
Scottish  poor,  and  they  show  that  the  general  health  of 
the  children  of  alcoholics  is  better  than  that  of  the  children 
of  sober  parents,  and  that  the  mental  defects  of  the  off- 
spring are  not  related  to  the  alcoholism  of  the  progenitors. 
From  many  sides  objections  have  been  raised  to  these  in- 
vestigators' conclusions.  It  is  impossible  here  to  discuss 
the  objections  in  detail,  but  they  have  shown  that  Pear- 
son's views  on  this  matter  cannot  be  accepted  without  re- 
serve. 

With  regard  to  this  question  of  the  importance  of  alco- 
hol, reference  is  also  made  to  the  fact  that  Jews  suffer  less 
from  epilepsy  than  members  of  other  races.  As  has  previ- 
ously been  shown,  it  is  very  generally  held  that  a  potent 
cause  of  epilepsy  is  alcoholic  intoxication  of  the  germ,  and 
the  comparative  exemption  of  Jews  from  epilepsy  is  sup- 
posed to  depend  upon  the  fact  that  the  members  of  this 
race  are  less  inclined  than  Gentiles  to  the  abuse  of  alcohol. 

It  is  also  maintained  that  children  actually  procreated 
when  the  parents  are  in  a  state  of  alcoholic  intoxication 
are  especially  apt  to  be  mentally  abnormal.  It  is,  however, 
extremely  difficult  to  obtain  adequate  evidence  bearing  on 
this  point,  and  the  existing  statistical  investigations  do  not 
suffice  to  justify  the  foregoing  statement. 

We  may  conclude  by  referring  to  one  good  example  fur- 
nished in  support  of  this  allegation,  in  which  a  woman 
married  to  a  healthy  man  procreated  healthy  children. 
After  his  death,  having  married  a  drunkard,  she  had  off- 
spring some  of  whom  were  epileptic. 

Against  this  and  similar  observations  the  objection  may 
be  made  that  the  mental  disorder  was  not  the  direct  out- 
come of  the  abuse  of  alcohol,  but  that  the  abuse  of  alcohol 


Significance  of  Diseases  to  Offspring  167 

was  merely  a  symptom  of  a  pre-existent  disturbance  in  the 
mental  faculties  and  that  it  was  this  disturbance  which  was 
transmitted  by  inheritance.  Unquestionably  this  is  pos- 
sible. The  view  receives  considerable  support  seeing  that 
the  tendency  to  drunkenness  is  itself  dependent  on  the  in- 
dividual's constitution.  A  great  many  persons  may  at  par- 
ticular periods  of  life  (for  example,  during  their  career 
as  students)  consume  considerable  quantities  of  alcohol  for 
a  long  time,  without  thereby  being  led  to  become  drunk- 
ards. There  is  needed  a  certain  ethical  inferiority  (which 
may,  of  course,  be  derived  from  drunkenness  in  the  par- 
ents) if  the  misuse  of  alcohol  is  to  become  truly  habitual. 
If,  therefore,  any  one  becomes  a  drunkard,  this  may  very 
often  depend  upon  his  primary  constitutional  abnormality, 
and  hence  his  children  may  also  be  abnormal.  The  misuse 
of  alcohol  is  then  merely  a  sign  of  the  pre-existing  abnor- 
mality. 

The  examination  of  certain  genealogical  trees  shows  that 
this  view  is  justified.  In  the  ancestry  of  families  who  now 
exhibit  alcoholic  tendencies  in  conjunction  with  mental 
disorder  we  sometimes  find  that  there  existed  mental  anom- 
alies before  a  family  tendency  to  the  misuse  of  alcohol  had 
become  apparent.  We  may  also  find  that  in  such  a  family, 
side  by  side  with  abnormal  individuals  who  are  drunkards, 
there  occur  other  abnormal  individuals  (especially  females) 
who  are  not  drunkards.  It  is  here  evident  that  mental 
disturbances  exist  as  family  peculiarities,  and  this  leads 
us  to  recognise  that  the  abuse  of  alcohol  by  the  drunken 
members  of  the  family  may  have  been  dependent  upon 
the  inherited  mental  disorder. 

The  following  consideration  must  also  be  given  due 
weight.  If  among  a  hundred  children  with  deficient  men- 
tal capacity  we  find  that  fifty  had  alcoholic  progenitors,  we 
may  presume  that  the  remaining  fifty  had  sober  parents. 
Such  children  can  therefore  be  procreated  in  the  absence 
of  any  alcoholic  influence.  How  is  it  possible  for  us  to  de- 
termine whether  the  parents  who  drank  to  excess  might 


168  Heredity,  Disease  and  Human  Evolution 

not  have  produced  children  with  deficient  intelligence  even 
if  they  had  not  themselves  been  addicted  to  the  abuse  of 
alcohol?  How  can  we  prove  that  the  drunkenness  was 
more  than  a  casual  accompaniment?  It  is  obvious  that 
definite  proof  is  hardly  obtainable.  Reference  must  again 
be  made  to  the  observation  that  the  children  of  alcoholics 
exhibit  greater  deficiencies  in  physique  and  character  than 
the  children  of  sober  parents,  and  that  there  is  good  reason 
for  referring  this  inferiority  to  the  efi'ects  of  alcohol.  But 
if  this  must  be  admitted,  it  must  also  be  recognised  as 
possible  that  the  deficient  mental  capacity  in  the  children 
of  alcoholics  owes  the  same  causation. 

As  regards  other  mental  disorders,  the  same  difficulties 
arise  as  in  the  case  of  children  exhibiting  deficient  intelli- 
gence. In  individual  cases  it  is  often  difficult  or  even  im- 
possible to  determine  whether  the  alcoholism  or  the  mental 
disease  is  the  primary  or  the  secondary  defect. 

We  may  sum  up  this  discussion  by  saying  that  while  the 
question  as  to  the  significance  of  alcoholism  in  causing  ger- 
minal intoxication,  and  thus  inducing  hereditary  disease, 
has  not  yet  been  answered  in  all  its  details,  in  view  of  the 
general  experience  of  the  poisonous  influence  of  alcohol 
(extending  also  to  the  reproductive  glands),  in  view  of 
the  results  of  experiments  on  animals,  and  in  view  of  sta- 
tistical records,  no  one  will  venture  altogether  to  deny  the 
injurious  influence  of  this  poison  upon  the  germinal  cells. 
In  any  case  we  must  regard  the  misuse  of  alcohol  as  a  nox- 
ious influence  competent  to  lead  to  the  production  of  hered- 
itary anomalies.  The  future  must,  however,  decide  whether 
the  opponents  of  alcohol  are  not  inclined  to  overstate  their 
case.  We  have  to  remember  that  among  many  nations  the 
use  of  alcohol  is  so  general  that  it  is  quite  exceptional  for 
any  male  adult  to  abstain  from  this  beverage,  and  that  its 
use  has  been  habitual  for  many  centuries.  If  the  pre- 
sumed germinal  intoxication  were  really  as  widespread  and 
as  severe  as  is  sometimes  asserted,  we  should  expect  the 
consequences  of  such  an  influence  to  be  far  graver  than 


Significance  of  Diseases  to  Offspring   169 

those  we  are  actually  able  to  observe.  More  comprehensive 
investigations  are  requisite  before  we  can  determine  with 
certainty  how  much  mischief  can  be  ascribed  to  the  use 
and  abuse  of  alcohol. 

To  sum  up,  in  conclusion,  the  results  of  our  inquiry  as 
to  the  genesis  of  hereditary  morbid  states,  we  are  forced 
to  the  general  conclusion  that  we  still  lack  adequate  infor- 
mation on  this  matter.  We  may,  indeed,  assume  that 
noxious  influences  of  all  kinds,  acting  on  the  germs 
through  the  intermediation  of  the  parents,  lead  to  altera- 
tions in  the  germinal  cells,  as  a  result  of  which  there  ap- 
pear in  the  children  pathological  conditions  susceptible  of 
further  transmission  by  inheritance.  When,  however,  we 
consider  the  case  of  individual  diseases,  we  find  that  there 
is  hardly  one  as  to  which,  in  this  respect,  we  possess  any 
tangible  knowledge.  Even  in  the  field  where  our  knowl- 
edge is  most  extensive,  namely  as  regards  the  effect  of  al- 
coholism in  originating  hereditary  mental  disorders,  far 
more  comprehensive  investigation  is  essential. 

7.     Increase  in  "Hereditary"  Diseases 

If  hereditary  diseases  continue  always  in  the  future  to 
be  transmitted  as  they  have  been  transmitted  in  the  past, 
the  number  of  sick  persons  must  go  on  increasing  con- 
comitantly with  the  increase  in  population.  The  relative 
proportion  of  sick  persons  to  the  population  might,  how- 
ever, remain  unchanged,  provided  that  no  new  diseases 
came  into  existence.  Is  this  likely  to  be  the  course  of 
events,  or  is  it  not  possible  that  there  may  be  a  gradual 
falling-off  in  inheritance,  leading  to  a  diminution  in  the 
amount  of  disease  ?    How  could  such  a  diminution  arise  ? 

First  of  all  it  is  possible  that  the  families  in  which  hered- 
itary diseases  prevail  may  die  out,  and  this  for  several 
reasons. 

It  is  by  no  means  rare  for  tainted  families  to  display 
an  exceptionally  high  child  mortality,  a  fa,ct  which  must 


170  Heredity,  Disease  and  Human  Evolution 

be  explained  upon  the  ground  that  the  conspicuous  hered- 
itary morbid  change  is  not  the  only  one,  but  that  the  bodies 
of  those  thus  affected  are  less  vitally  efficient,  that  they 
have  suffered  some  general  injury  in  consequence  of  the 
pathological  condition.  For  example,  we  see  something  of 
this  kind  in  hemophilia,  although  in  families  affected  with 
this  disease  the  high  child  mortality  is  partially  compen- 
sated by  an  unusually  high  birthrate  (see  p.  130), 

A  similar  excessive  child  mortality  existed  in  the  family 
characterised  by  hypotrichosis  (p.  146).  In  one  branch 
of  this  family  in  which  there  were  fourteen  children  one 
only  attained  to  reproduction.  Moreover,  at  the  time  when 
E.  Fischer  made  his  investigation,  there  were  still  alive 
belonging  to  this  family  no  more  than  two  individuals, 
both  in  poor  health,  and  both  over  forty  years  of  age,  and 
therefore  likely  to  remain  childless.  In  that  event  the 
morbid  condition  characteristic  of  this  family  would  have 
completely  died  out. 

A  second  possibility  is  that  the  diseased  individuals  will 
not  marry,  being  shunned  on  account  of  their  condition. 
Those  with  marked  malformations  will  seldom  find  a  mate, 
and  the  same  is  true  of  those  suffering  from  mental  disor- 
der, etc.  This  happened  in  the  family  whose  members  were 
affected  with  hypotrichosis,  for  many  of  them  remained 
unmarried. 

We  have  thirdly  to  take  into  consideration  that  many  of 
those  affected  with  hereditary  disease  are  incompetent  for 
reproduction.  This  applies  more  or  less  completely  to  se- 
vere eases  of  alcoholism,  mental  disorder,  diabetes,  etc. 

For  the  reasons  named,  tainted  families  may  die  out  in 
the  course  of  a  few  generations. 

There  is,  however,  a  further  possibility.  The  morbid 
state  may  be  suppressed  in  consequence  of  marriage  with 
a  thoroughly  healthy  and  vigorous  individual  from  an 
untainted  stock.  It  has  again  and  again  been  recorded 
that  when  a  member  of  some  family  affected  with  hered- 
itary  taint  has   married   a  healthy   person,   the   morbid 


Significance  of  Diseases  to  Offspring  171 

heredity  has  come  to  an  end  in  this  branch,  the  offspring 
remaining  healthy.  Here  the  healthy  constitution  must 
have  been  the  more  powerful  one,  and  must  have  overcome 
the  hitherto  dominant  pathological  tendency.  We  must 
interpret  this  in  the  sense  that  the  morbid  character  no 
longer  remained  independent,  no  longer  underwent  segre- 
gation, but,  permanently  united  with  the  healthy  charac- 
ter, was  no  longer  able  to  maintain  a  separate  existence. 
It  may  ultimately  have  undergone  atrophy  and  completely 
disappeared.  This  view  is  more  acceptable  than  the  other, 
that  the  morbid  tendency  had  merely  been  weakened  in 
contrast  with  the  healthy  one,  that  the  former  had  simply 
become  recessive.  For  even  though  recessive,  it  would 
have  continued  to  manifest  itself  in  a  small  percentage  of 
the  offspring.  It  is  on  the  first  assumption  that  we  can  best 
understand  how  through  marriage  with  healthy  persons, 
the  morbid  heredity  may  occasionally  arrive  at  its  term. 
Still,  we  have  also  to  take  into  account  the  alternative 
hypothesis,  that  the  pathological  tendency  may  merely  have 
become  recessive,  for  in  view  of  the  small  proportion  of  the 
human  germinal  cells  that  attain  to  fertilisation,  it  is  pos- 
sible for  a  recessive  character  to  disappear  from  sight  for 
several  generations,  and  then  to  reappear.  But  this  also 
would  signify  a  notable  diminution  in  the  number  of  cases 
of  disease. 

When,  however,  we  proceed  to  ask  whether  a  general 
diminution  of  hereditary  morbid  conditions  is  likely  to 
be  brought  about  by  the  dying  out  of  diseased  families, 
and  by  intermarriage  between  the  members  of  such 
families  and  those  of  healthy  stock,  we  are  unable,  since 
new  diseases  are  continually  arising,  to  return  a  confident 
answer.  The  conditions  just  described  have  always  ob- 
tained, and  if  they  could  exercise  any  effective  influence 
in  the  desired  direction,  some  improvement  should  already 
have  resulted.  Nothing  of  the  kind  has  taken  place,  and 
we  could  only  hope  to  attain  good  by  such  means  if  in  the 
future  we  could  deliberately  intensify  their  employment 


172  Heredity,  Disease  and  Human  Evolution 

in  order  to  secure  a  diminution  in  the  extent  of  morbid 
inheritance.     Of  this  we  shall  speak  in  the  sequel. 

First,  however,  we  must  once  more  draw  attention  to 
the  fact  that  the  disappearance  of  diseases  through  dying 
out  and  through  intermarriage  with  healthy  stocks  may 
be  apparent  merely.  As  we  have  shown  above,  a  hereditary 
morbid  state  may  remain  latent  for  one  or  many  genera- 
tions, and  then  recur  as  an  atavistic  manifestation.  This 
possibility  is  established  by  numerous  family  histories,  in 
which  hereditary  disease  skips  entire  generations.  It  fol- 
lows that  hereditary  diseases  would  not  necessarily  disap- 
pear for  ever  if  we  were  to  kill  off  all  the  individuals  who 
were  demonstrably  affected.  The  offspring  already  procre- 
ated by  these  individuals,  bearing  the  disease  in  a  latent 
form,  would  transmit  the  abnormal  taint  to  subsequent 
generations.  At  some  subsequent  period,  when  for  un- 
known reasons  the  abnormality  gains  the  upper  hand  over 
the  healthy  quality  and  becomes  dominant,  or  when  the 
recessive  morbid  character  becomes  spontaneously  manifest 
(especially  when  the  number  of  the  offspring  is  large),  the 
disease  reappears.  This  is  especially  likely  to  occur  if  two 
individuals  with  identical  disease-rudiments  unite  in  pro- 
creation. It  may  ensue  in  the  marriage  of  near  kin,  but 
also  in  the  intermarriage  of  members  of  different  families 
affected  with  the  like  hereditary  taint. 

The  former  possibility,  that  of  in-and-in  breeding,  re- 
quires closer  examination. 

In  perfectly  healthy  families  (that  is  to  say,  in  families 
that  are  really  free  from  all  hereditary  taint,  and  not 
merely  free  in  appearance  at  the  time  of  examination),  the 
marriage  of  near  kin,  if  not  too  frequently  repeated,  is 
without  ill  effect.  Observations  on  human  beings  and  ex- 
periments on  animals  establish  this  clearly. 

E.  Fischer  reports  the  history  of  a  half  caste  tribe  of 
Bosjesmen  and  Hottentots,  among  whom  in-and-in  breed- 
ing had  continued  for  seven  generations.  The  2,500  indi- 
viduals  composing  this   tribe   were   thoroughly   healthy. 


Significance  of  Diseases  to  Offspring   173 

There  were  no  signs  of  degeneration.  The  birth-rate  was 
comparatively  high,  and  the  child-mortality  was  no  greater 
than  among  the  neighbouring  whites.  Poeh  similarly  re- 
ports that  in  a  Papuan  tribe  living  in  complete  isolation, 
in-and-in  breeding  had  not  led  to  the  appearance  of  any 
degenerative  consequences. 

Such  experiences  are  in  conflict  with  the  views  generally 
prevalent  to-day,  for  the  common  idea  is  that  in-and-in 
breeding  must  necessarily  lead  to  injurious  results.  But 
this  opinion  has  not  always  prevailed.  Abraham  married 
his  half-sister  without  hesitation.  In  ancient  Egypt,  mar- 
riages between  brothers  and  sisters  were  common,  espe- 
cially in  the  case  of  the  Ptolemies,  among  whom  are  on 
record  thirteen  marriages  between  brother  and  sister,  one 
between  half-brother  and  half-sister,  and  two  between 
uncle  and  niece.  In  Athens,  again,  marriages  between 
brother  and  sister  were  not  infrequent.  The  aversion  from 
such  unions  to-day  is  sometimes  supported  by  reference  to 
the  experience  of  breeders,  who  have  in  many  cases  seen 
injurious  consequences  from  long-continued  in-and-in 
breeding.  Chapmann  reports  the  following  experiment.  He 
reared  500  chickens  in  an  incubator,  and  found  that  50  of 
these  grew  no  feathers;  they  remained  callow  and  soon 
succumbed.  He  referred  this  to  the  fact  that  their  pro- 
genitors had  bred  in-and-in  for  four  years. 

But  there  exist  records  of  experiments  which  point  to 
the  opposite  conclusion.  Chapeaurouge  records  studies  on 
thoroughbred  horses,  among  whose  progenitors  in-and-in 
breeding  had  been  frequent,  and  considers  that  this  practice 
accounts  for  the  remarkable  qualities  of  the  race-horse. 
This  view  was  supported  by  the  observation  that  celebrated 
stallions  sometimes  procreated  inferior  stock,  but  only 
when  crossed  with  unrelated  mares.  From  this  we  may 
infer  that  in-and-in  breeding  may  lead  to  an  intensification 
of  the  distinctive  characters  of  particular  stocks  of  animals, 
provided  always  the  individuals  thus  in-bred  are  perfectly 
healthy  in  other  respects. 


174  Heredity,  Disease  and  Human  Evolution 

In  the  ease  of  reigning  and  noble  families  in-and-in 
breeding  is  also  believed  to  have  led  to  an  intensification 
of  their  striking  talents. 

We  may  therefore  go  so  far  as  to  say  that  individual 
marriages  of  near  kin  belonging  to  a  healthy  stock  are 
altogether  free  from  objection.  It  is  not  the  marriage  be- 
tween members  of  a  normal  family  that  can  prove  injuri- 
ous to  the  offspring,  but  the  marriage  of  near  kin  belong- 
ing to  families  in  which  hereditary  morbid  states  prevail, 
or  have  prevailed  in  earlier  generations. 

It  is  true  that  we  find  genealogical  trees  and  pedigrees  in 
which  marriages  of  near  kin  have  occurred  for  several  gen- 
erations without  disease  resulting,  but  in  later  generations, 
when  members  of  the  family  have  intermarried,  abnormal 
offspring  have  been  procreated.  It  might  seem  in  these 
cases  as  if  the  repeated  intermarriages  of  blood-relatives 
had  ultimately  led  to  the  production  of  disease,  although 
the  family  was  primarily  healthy.  A  more  probable  as- 
sumption, however,  is  that  the  disease  was  already  latent 
in  the  family,  and  underwent  concentration  through  in- 
and-in  breeding.  In  many  cases,  support  to  such  a  view 
is  given  by  the  observation  that  in  other  branches  of  the 
family  the  same  disease  appears  in  the  absence  of  in-and-in 
breeding. 

The  effect  of  the  marriage  of  near  kin  is  conspicuous  in 
the  pedigree  of  Don  Carlos,  son  of  Philip  II  of  Spain.  His 
paternal  grandfather  and  his  maternal  grandmother  were 
brother  and  sister  and  their  mother  was  Juana  the  Mad. 
His  paternal  grandmother  and  maternal  grandfather  were 
also  brother  and  sister.  Thus  instead  of  eight  great-grand- 
parents he  had  four  only.  These  four  great-grandparents,  in 
their  turn,  instead  of  being  derived  from  eight  different 
couples  and  sixteen  individuals  in  the  previous  genera- 
tion, were  derived  from  three  couples  only  and  six  individ- 
uals, so  that  the  blood-relationship  among  the  ancestry  was 
extraordinarily  close. 

The  pedigree  of  Louis  II  of  Bavaria  also  shows  numer- 


Significance  of  Diseases  to  Offspring  175 

ous  marriages  of  near  kin.  In  the  fifth  generation  back 
are  three  male  ancestors  derived  from  tainted  families,  one 
of  these  being  on  the  paternal  and  the  other  two  on  the 
maternal  side.  On  the  latter  side  of  the  pedigree,  we  also 
find  in  earlier  generations  that  mental  disease  manifested 
itself  several  times,  having  been  concentrated  by  the  mar- 
riage of  near  kin.  Moreover,  numerous  members  of  the 
family  displayed  more  or  less  marked  mental  abnormality. 

In  certain  pedigrees  and  genealogical  trees,  while  it  is 
true  that  there  occur  marriages  of  near  kin  leading  to  the 
procreation  of  offspring,  in  other  branches,  where  the  mar- 
riages have  not  been  between  blood-relations,  there  are  so 
many  diseased  individuals,  that  on  a  review  of  the  whole 
it  is  hardly  possible  to  suppose  that  in-and-in  breeding  has 
exercised  any  notable  influence.  We  cannot,  indeed,  doubt 
that  the  offspring,  in  such  cases,  of  the  marriage  of  near 
kin  are  tainted  on  both  sides,  and  that  they  are  therefore 
especially  liable  to  inherit  the  taint.  But  a  study  of  such 
genealogical  trees  shows  us  that  even  without  in-and-in 
breeding  the  extensive  hereditary  transmission  of  disease 
may  occur. 

Marriage  between  individuals  who  are  not  related  but 
who  are  hereditarily  affected  with  the  identical  taint  may 
naturally  have  the  same  effect  as  the  marriage  of  two 
members  of  a  tainted  family  in  awakening  a  latent  taint 
or  in  intensifying  a  morbid  condition  that  is  already  mani- 
fest. This  is  true,  in  especial,  of  mental  disorders,  with 
or  without  the  association  of  alcoholism.  Intermarriage 
between  members  of  families  thus  tainted  leads  to  a  con- 
centration, to  an  intensification  of  the  pathological  state 
(see  p.  135). 

In  the  marriage  of  near  kin,  and  in  the  marriage  of 
persons  affected  with  the  same  hereditary  taint,  we  must 
recognise  factors  of  the  utmost  importance  for  the  pro- 
gressive inheritance  of  abnormal  qualities.  Both  these  fac- 
tors counteract  the  tendency  to  the  dying  out  of  hereditary 
diseases. 


176  Heredity,  Disease  and  Human  Evolution 

The  efficacy  of  these  factors  is  even  greater  than  may 
appear  at  first  sight. 

As  far  as  concerns  the  marriage  of  near  kin  in  those 
families  in  which  the  morbid  tendency  is  plainly  manifest, 
we  might  hope  for  good  results  by  discouraging  such  mar- 
riages. But  the  pathological  disposition  may  be  latent,  and 
may  have  failed  to  display  itself  for  several  generations. 
If,  then,  as  is  commonly  the  case,  no  information  is  avail- 
able concerning  the  illnesses  of  remote  progenitors,  the 
family  may  be  supposed  to  be  healthy,  and  it  may  be  con- 
sidered that  there  is  no  objection  to  the  proposed  mar- 
riage. Thus  it  is  possible,  and  doubtless  often  happens, 
that  after  the  marriage  of  near  kin,  especially  when  such 
marriages  are  repeated  several  times  in  the  same  family,  a 
disease  will  unexpectedly  come  to  light  in  a  stock  that  was 
apparently  intact. 

Again,  the  kinship  of  human  beings  is  far  more  intimate 
than  is  shown  by  pedigrees,  for  these  never  refer  to  more 
than  a  limited  number  of  persons  of  earlier  generations. 
For  example,  from  the  ancestors  of  persons  now  living,  if 
we  go  back  so  far  only  as  five  generations,  there  must  have 
sprung  a  great  many  descendants  whose  blood-relationship 
to  the  persons  of  this  generation  is  completely  ignored,  but 
to  whom  a  formerly  prevalent  morbid  condition  may  natu- 
rally have  been  transmitted  in  a  latent  form.  A  marriage 
between  two  such  individuals  erroneously  believed  to  be 
unrelated  may  lead  to  the  reappearance  of  the  disease  in 
an  active  form.  Very  little  reflection  upon  such  conditions 
will  show  that  it  is  extremely  difficult,  and  may  be  alto- 
gether impossible,  to  ascertain  whether  persons  supposed 
to  be  unrelated  may  not  really  harbour  identical  disease- 
rudiments.  Accurate  information  on  this  point  could  be 
furnished  only  by  complete  pedigrees,  extending  back  for 
numerous  generations,  of  all  persons  now  living,  enabling 
us  to  demonstrate  the  mutual  kinships  of  all  of  these. 
With  the  means  now  at  our  disposal  the  establishment  of 
such  comprehensive  pedigrees  is  quite  impossible.    The  iso- 


Significance  of  Diseases  to  Offspring  177 

lated  families  as  to  which  data  are  available  constitute 
to-day  an  infinitesimal  number  of  exceptions.  The  excep- 
tions are  confined  almost  exclusively  to  the  families  of 
those  whose  members  have  been  prominent  in  public  life, 
and  whose  family  records  have  for  this  reason  been  care- 
fully kept. 

While,  then,  it  cannot  be  doubted  that  in-and-in  breed- 
ing and  the  marriage  of  persons  affected  with  the  same 
taint  favour  the  diffusion  of  hereditary  diseases,  we  have 
now  to  show  that  the  like  significance  has  been  ascribed 
to  another  factor,  whose  possible  importance  might  be  over- 
looked, namely  hygiene.  The  primary  aim  of  hygiene,  and 
one  that  appears  to  be  on  all  hands  successfully  attained, 
is  to  limit  the  prevalence  of  epidemic  diseases.  Among 
these  may  be  mentioned  the  well-known  diseases  of  child- 
hood (measles,  scarlatina,  diphtheria,  the  intestinal  disor- 
ders of  infants,  etc.),  and  also  tuberculosis. 

It  has  been  said  that  the  infectious  diseases  of  childhood 
we  have  named  carry  off  by  preference  weakly  individuals, 
those  who  biologically  are  of  deficient  value,  and  conse- 
quently many  of  those  who  are  hereditarily  tainted.  This 
is  said  to  be  a  good  thing.  Thus,  it  is  contended,  our  race 
is  freed  from  worthless  members,  and  only  the  vitally  eflB- 
cient  survive.  Hygiene,  therefore,  is  a  bad  thing,  for  it 
interferes  with  this  selective  process,  and  promotes  the 
survival  of  the  weakly. 

Less  weight  would  have  been  attached  to  this  objection 
if  due  consideration  had  been  given  to  the  fact  that  hygiene 
is  a  new  acquisition,  and  that  for  this  reason  the  selective 
process  with  which  hygiene  is  now  supposed  to  interfere 
must  have  been  going  on  vigorously  for  many  thousands 
of  years.  But,  as  every  one  can  see,  the  results  have  been 
far  from  satisfactory,  for  if  it  were  otherwise  the  continu- 
ance of  the  process  would  hardly  now  be  necessary. 

There  are,  however,  other  arguments  by  which  such  at- 
tacks upon  hygiene  may  be  answered.  The  statement  is 
incorrect,  or  at  any  rate  unproved,  that  epidemic  diseases 


178  Heredity,  Disease  and  Human  Evolution 

affecting  childhood  lead  to  the  death,  for  the  most  part, 
of  the  less  vitally  efficient  individuals.  There  is  no  neces- 
sary relationship  between  the  predisposition  to  the  various 
infections  and  the  constitution  of  the  body  in  other  re- 
spects. It  is  certain  that  the  existence  of  mental  disorders, 
malformations,  hemophilia,  colour-blindness,  and  other 
anomalies  of  the  eyes  and  of  the  skin,  does  not  justify  us 
in  assuming  the  concomitant  existence  of  a  deficient  power 
of  resistance  to  infectious  disease.  It  may  be  suggested 
that  such  a  deficient  resisting-power  would  at  least  be 
found  in  children  suffering  from  general  bodily  weakness; 
but  in  actual  experience  we  do  not  find  that  such  children 
are  especially  liable  to  suffer  from  the  epidemic  diseases. 

It  remains  to  consider  the  case  of  tuberculosis.  It  has 
been  contended  that  children  affected  with  this  disease  are 
preferentially  carried  off  by  the  acute  infections.  This, 
however,  is  by  no  means  the  case.  Those  who  have  occa- 
sion to  make  frequent  post-mortems  on  the  bodies  of  chil- 
dren who  have  succumbed  to  infectious  diseases  fail  to  find 
in  such  cases  any  marked  prevalence  of  tuberculosis.  Very 
often  the  children  appear  to  have  been  exceptionally  vig- 
orous. 

It  must  therefore  be  admitted  that  the  idea  that  epi- 
demic diseases  exercise  a  valuable  selective  influence  on 
our  race  is  erroneous.  On  the  other  hand,  it  has  often 
been  overlooked  that  such  diseases  may  exercise  a  most  un- 
favourable influence  by  leading  to  new  injuries  to  the  ger- 
minal cells.  In  these  infections  the  entire  organism  is  in- 
jured by  the  poisonous  substances  produced  by  the  micro- 
organisms which  are  the  actual  causes  of  disease.  The 
toxins  may  injuriously  affect  the  germinal  cells.  This  pos- 
sibility applies  above  all  to  tuberculosis,  which  involves 
very  severe  injury  to  the  whole  body. 

Hygiene,  however,  which  aims  at  and  successfully  effects 
a  reduction  in  the  prevalence  of  epidemic  disease,  neces- 
sarily counteracts  such  injurious  influences  affecting  the 
germinal  cells.    Hence,  for  this  reason  also,  we  must  desire 


Significance  of  Diseases  to  Offspring  179 

the  greatest  possible  reduction  in  the  prevalence  of  infec- 
tious diseases. 

We  also  have  to  remember  that  the  children  who  have 
suffered  from  some  acute  infection,  even  if  they  were  per- 
fectly healthy  at  the  outset,  and  were  therefore  among 
those  whose  survival  is  to  be  regarded  as  especially  desir- 
able, are  often  permanently  injured  by  the  acute  infec- 
tion, sustaining  damage  to  the  kidneys,  to  the  heart,  to  the 
blood-vessels,  etc. 

We  must  bear  this  in  mind  as  we  pass  to  the  following 
considerations. 

If  it  were  true  that  high  child-mortality  were  selective 
in  its  working,  we  should  expect  to  find  that  in  those 
regions  in  which  such  a  high  mortality  usually  prevailed 
the  survivors  would  be  exceptionally  vigorous.  One  of 
several  ways  in  which  such  exceptional  vigour  might  be 
expected  to  manifest  itself  would  be  in  the  percentage  of 
those  found  fit  for  military  service,  and  this  ought  to  be 
greater  in  these  regions  than  in  those  where,  in  consequence 
of  a  lower  child-mortality,  the  selective  influence  had  not 
been  in  operation.  It  is  not,  however,  possible  to  ascertain 
the  existence  of  any  such  relationship.  On  the  contrary, 
the  records  show  that  there  is  less  fitness  for  military 
service  precisely  in  those  regions  where  child-mortality  is 
high.  Provided  these  statistical  inquiries  are  based  upon 
a  sufficiently  firm  foundation,  the  inference  would  be  that 
epidemic  diseases  had  not  exercised  a  favourable  selective 
influence,  and  that  the  survivors  had  been  injured  by  dis- 
ease. 

Thus  it  is  on  the  whole  quite  without  justification  that 
hygiene  is  reproached  with  keeping  the  less  fit  alive  and 
thus  leading  to  an  increase  in  "hereditary  diseases. 

The  case  is  somewhat  different  as  regards  another  factor 
which  has  been  similarly  blamed,  namely  the  care  of  the 
sick.  There  can  be  no  doubt  that  such  care  keeps  alive 
numerous  individuals  who  are  below  par  value  from  the 
outlook  of  heredity,  far  longer  than  they  would  have  been 


180  Heredity,  Disease  and  Human  Evolution 

able  to  live  in  the  absence  of  such  care,  and  that,  in  con- 
sequence of  this,  there  frequently  arises  the  danger  that 
such  persons  will  reproduce  their  kind  and  procreate  dis- 
eased children.  Are  we  for  this  reason  to  leave  such  per- 
sons uncared  for,  in  order  that  they  may  succumb  the 
sooner  ?  The  author  is  not  to  be  understood  as  making  any 
such  recommendation.  In  our  efforts  to  promote  the  fur- 
ther evolution  of  humanity  we  are  all  dependent  one  upon 
the  other,  and  this  sense  of  solidarity  extends  also  to  the 
invalids  of  whom  we  are  now  speaking.  To  such  sufferers, 
who  are  not  responsible  for  their  own  condition,  we  must 
give  our  best  attention,  and  we  shall  do  so  the  more  gladly 
the  nearer  they  are  to  us.  Doubtless  we  cannot  fail  to 
know  that  it  would  be  better  if  they  did  not  exist,  but 
once  they  do  exist  we  must  assume  responsibility  for  them. 
As,  however,  we  keep  them  alive,  it  is  necessary,  since  we 
must  avoid  by  all  means  in  our  power  an  interference  with 
the  evolution  of  our  race,  that  we  should  take  care  that 
patients  suffering  from  hereditary  disease  shall  not  propa- 
gate their  kind.  To  this  matter  we  shall  return  in  the 
ninth  chapter.  We  have  previously  shown  that  we  are 
forced  to  care  for  an  extraordinarily  large  number  of  per- 
sons who  will  never  again  be  functionally  efficient,  and  this 
applies  above  all  to  severe  cases  of  mental  disorder.  The 
necessity  involves  severe  injury  to  our  race,  but  the  indi- 
viduals in  question  are  as  a  rule  no  longer  likely  to  pro- 
create. 

We  conclude  that  the  diffusion  of  hereditary  pathological 
states  is  promoted  by  in-and-in  breeding,  by  the  intermar- 
riage of  individuals  affected  with  the  same  hereditary  taint, 
and  by  the  care  we  give  to  those  suffering  from  hereditary 
disease  unless  we  prevent  such  individuals  from  procreat- 
ing. 

We  have  also  to  take  into  consideration  the  genesis  of 
new  germinal  diseases,  especially  in  consequence  of  intoxi- 
cation of  the  germ,  by  alcohol  and  other  poisons  artificially 


Significance  of  Diseases  to  Offspring  181 

introduced  from  without,  and  also  by  the  toxins  formed  in 
the  course  of  the  infectious  diseases. 

There  thus  unquestionably  exists  a  danger  of  the  in- 
crease of  hereditary  diseases.  Is  the  tendency  in  this  direc- 
tion stronger  than  are  those  tendencies  which  are  favour- 
able to  a  diminution  in  the  prevalence  of  such  diseases? 
This  question  will  be  considered  in  the  next  section. 

8.     Is  the  Human  Race  Degenerating? 

If  the  hereditary  diseases  were  continually  increasing, 
the  percentage  of  individuals  invalided  from  the  start, 
tainted  in  their  innermost  being,  would  also  continually 
increase.  Within  a  time  not  so  extremely  remote,  their 
number  would  become  so  great  that  the  continued  effective 
existence  of  our  race  would  become  a  difficult  matter.  Ul- 
timately there  would  no  longer  be  any  healthy  persons. 

Such  an  increasing  functional  incapacity  of  the  human 
race  is  assumed  to  be  possible,  and  is  denoted  by  the  term 
degeneration.  We  have  to  ask  whether  the  contingency 
need  seriously  be  anticipated. 

We  must  first  of  all  make  it  clear  that  as  far  as  degen- 
eration is  concerned  it  is  only  the  hereditary  diseases  that 
can  play  a  part.  All  other  diseases  than  these,  however 
destructive  they  may  be,  whether  they  induce  speedy  death 
or  prolonged  illness,  have  nothing  to  do  with  degeneration. 
They  do  not  involve  any  increasing  deterioration  of  the 
human  race  as  a  whole.  They  do  not  attack  the  founda- 
tions of  the  human  constitution,  or  rather  they  operate 
in  this  direction  only  in  so  far  as  they  exert  an  injurious 
influence  upon  the  germinal  cells  and  thus  give  rise  to 
hereditary  anomalies.  If  they  do  not  do  this  they  do  not 
produce  degeneration. 

Moreover,  not  all  hereditary  morbid  states  contribute  in 
equal  degree  to  the  presumed  increasing  constitutional 
deterioration.  The  slighter  malformations,  such  as  the 
hereditary  absence  of  one  of  the  fingers,  involve  no  disad- 


182  Heredity,  Disease  and  Human  Evolution 

vantage  to  the  race.  Other  anomalies,  such  as  those  of 
the  skin  and  the  hair,  play  an  unimportant  part.  There 
are  others,  however,  such  as  colour-blindness  and  short- 
sightedness, which  are  plainly  degenerative  in  character. 
The  most  important  of  all,  in  this  connexion,  are  disturb- 
ances of  the  nervous  system,  and  especially  all  kinds  of 
mental  disorder  (including  criminality).  The  increase  in 
these  would  depress  mankind  to  a  continually  lower  level, 
would  involve  the  degeneration  of  the  race. 

What  have  we  to  say  about  such  a  constitutional  deterio- 
ration of  the  human  species? 

In  the  last  section  we  showed  that  many  circumstances 
favour  an  increase  in  hereditary  diseases,  but  that  others 
counteract  this.  Since  it  is  impossible  to  determine  on 
purely  theoretical  grounds  whether  one  set  of  influences 
or  the  other  will  predominate,  we  must  seek  light  from 
positive  experience.  Can  it,  in  fact,  be  demonstrated  that 
hereditary  diseases  are  on  the  increase?  Those  who  have 
studied  the  subject  return  conflicting  answers. 

Riidin,  among  others,  contends  that  there  is  increasing 
degeneration.  He  is  of  opinion  that  suicide,  which  is  cer- 
tainly in  great  part  dependent  upon  mental  anomalies,  is 
on  the  increase;  psychopaths,  neurasthenics,  and  certain 
types  of  criminals,  are  becoming  commoner  ;  that  alcoholism 
with  all  the  disturbances  to  which  it  gives  rise,  is  on  the 
increase;  that  diabetes  and  the  incapacity  of  women  to 
suckle  their  children  are  both  becoming  more  generally 
diffused.  He  refers  also  to  the  decline  in  the  birth-rate,  in 
the  production  of  which  decline  a  degenerative  factor  co- 
operates; and,  finally,  to  the  increase  of  accidental  neu- 
roses and  in  unfitness  for  military  service.  The  two  phe- 
nomena last  named  must  not,  however,  be  unconditionally 
included  under  the  head  of  degeneration.  The  accidental 
neuroses  are  acquired  in  consequence  of  individual  injury, 
and  are  not  therefore  transmissible  to  the  offspring.  As 
regards  unfitness  for  military  service,  this  is  due,  not  only 
to  constitutional  hereditary  peculiarities,  but  also  to  all 


Significance  of  Diseases  to  Offspring   183 

kinds  of  acquired  anomalies  which  have  not  been  derived 
by  inheritance  from  the  parents. 

Kraepelin  also  favours  the  view  that  degeneration  is  in 
progress.  He  refers  especially  to  the  increase  in  disease 
among  the  American  negroes,  who  suffer  more  and  more 
from  alcoholism  and  softening  of  the  brain. 

Other  students  of  the  question  hold  the  converse  view. 
Wilmanns,  for  example,  considers  it  questionable  if  racial 
degeneration  is  in  progress.  As  to  the  alleged  evidence 
afforded  by  the  increase  in  mental  diseases,  he  points  out 
that  all  that  has  really  occurred  is  an  increased  accumula- 
tion of  mental  patients  in  asylums.  Those  suffering  from 
minor  degrees  of  mental  disorder  who  were  formerly  kept 
at  home  now  receive  institutional  care  because  asylum  con- 
ditions are  greatly  improved.  A  real  increase  in  the  num- 
ber of  mental  patients  could  be  proved  only  by  a  general 
census  including  all  varieties  of  mental  disorder,  but  no 
such  census  has  hitherto  been  made.  It  cannot  be  denied 
that  there  is  an  increase  in  neuroses,  but  this  does  not 
signify  degeneration,  for  illnesses  of  this  character  are 
not  hereditary. 

Weber  also  regards  as  untrustworthy  the  statistical  evi- 
dence derived  from  the  number  of  mental  cases  receiving 
institutional  care.  It  seems  to  him  that  the  severer  forms 
of  mental  disorder  have  become  less  frequent,  and  he  is 
therefore  of  opinion  that  the  earlier  pessimistic  views  as 
to  the  occurrence  of  degeneration  are  no  longer  justified. 
Weber  further  makes  special  reference  to  the  experience 
that  the  marriage  of  an  invalid  with  a  perfectly  healthy 
individual  may  be  followed  by  the  procreation  of  normal 
children. 

These  opposing  views  cannot  at  present  be  harmonised. 

It  is  obvious  that  if  a  process  of  degeneration  be  really 
in  progress,  the  importance  of  hereditary  diseases  is  even 
greater  than,  would  otherwise  be  the  case,  and  that  man- 
kind, under  pain  of  racial  destruction,  must  make  all  pos- 
sible efforts  to  put  a  stop  to  the  threatening  diffusion  of 


184  Heredity,  Disease  and  Human  Evolution 

pathological  conditions.  But  even  if  degeneration  be  not 
a  fact,  if  there  be  no  increase  in  hereditary  morbid  states, 
if  the  number  of  diseases  remain  the  same  apart  from  any 
interference  of  ours,  the  disadvantages  that  the  existence 
of  these  diseases  involve  are  so  enormous  that  we  have  the 
greatest  possible  interest  in  endeavouring  to  diminish  their 
prevalence. 


CHAPTER  VII 

CAN  DISEASE  FAVOUR  HUMAN  EVOLUTION?      TELEOLOGY 

Since  disease,  as  we  showed  in  the  introductory  chapter, 
always  involves  a  diminution  in  functional  capacity,  it  is 
not  to  be  expected  that  that  which  damages  the  individual 
will  be  likelj  to  favour  mankind  as  a  whole.  The  morbid 
change  which  affects  any  portion  of  the  body  remains  mor- 
bid even  if  it  be  transmitted  by  inheritance  through  count- 
less generations  and  to  innumerable  individuals.  It  seems 
conceivable,  however,  that  human  beings  might,  in  the 
course  of  centuries,  become  habituated  to  a  pathological 
state,  in  the  sense  that  the  functional  activity  that  has  been 
depressed  in  consequence  of  the  existence  of  that  state  might 
be  taken  over  by  another  organ,  so  that  the  changed  portion 
of  the  body  would  no  longer  possess  a  disease-producing 
significance.  He  may  imagine  that  in  that  ease,  by  persis- 
tent inheritance,  there  might  be  produced  groups  of  human 
beings  distinguished  from  the  rest  of  the  race  by  the  de- 
pressed functional  activity  of  one  organ  and  the  increased 
functional  activity  of  another,  thus  constituting  a  peculiar 
species  of  mankind.  We  may  ask,  therefore,  in  this  connex- 
ion, whether  diseases  do  actually  lead  to  the  origin  of  new 
species,  whether  they  may  transform  humanity  in  particu- 
lar directions,  and  perchance  promote  a  desirable  evolution. 

A  like  assumption  has  been  made  in  the  case  of  animals. 
For  example,  some  persons  have  believed  that  dachshunds 
came  into  existence  in  this  way,  that  rickets  in  the  first 
instance  caused  the  characteristic  atrophy  of  the  extremi- 
ties, and  that  this  change  was  subsequently  transmitted  by 
inheritance.    This  view  is  erroneous.    As  von  Hansemann 

185 


186  Heredity,  Disease  and  Human  Evolution 

has  shown,  the  peculiar  formation  of  the  legs  in  dachshunds 
has  nothing  whatever  to  do  with  rickets  or  with  any  other 
disease,  and  is  a  characteristic  of  this  particular  race  of 
dog  on  the  same  footing  as  the  characteristics  of  other 
breeds  of  animals. 

On  the  other  hand,  the  peculiar  characteristic  of  crested 
fowls  and  crested  tufted  ducks,  in  which  there  exists  a 
rounded  prominence  on  the  head,  representing  a  kind  of 
cerebral  hernia,  must  be  regarded  as  pathological.  For  in 
these  cases  we  have  a  protrusion  of  the  vault  of  the  skull, 
containing  a  portion  of  the  brain.  It  is,  indeed,  distin- 
guished from  cerebral  hernia  in  human  beings  by  the  fact 
that  the  brain  remains  covered  by  a  bony  wall;  there  is 
no  hole  in  the  skull  through  which  the  cerebral  tissue 
projects.  Nevertheless,  the  condition  is  altogether  morbid, 
and  even  though  the  birds  thus  affected  have  a  distinctive 
appearance  and  seem  to  constitute  a  separate  race,  they 
must  not  really  be  regarded  in  this  way.  As  compared 
with  individuals  that  do  not  exhibit  the  malformation,  they 
are  always  below  par  value,  and  they  manifest  all  kinds 
of  morbid  disturbances.  There  is  no  question  here  of  the 
constitution  of  a  new  species. 

As  regards  the  human  race,  we  know  of  no  example 
which  can  be  interpreted  in  such  a  sense.  Pathological 
changes  remain  pathological  throughout  the  generations, 
and  although  it  is  true  that  certain  abnormal  conditions, 
such  as  hereditary  Polydactyly,  do  no  particular  harm,  it 
will  not  occur  to  any  one  to  regard  persons  thus  affected 
as  constituting  a  separate  species.  Still  less  will  any  one 
be  inclined  to  see  in  this  malformation  a  peculiarity  favour- 
ing the  evolution  of  the  race,  or  the  particular  group  of 
those  who  are  affected.  If  these  considerations  apply  to 
simple  and  on  the  whole  harmless  anomalies,  a  fortiori 
they  will  apply  to  really  morbid  changes. 

While  the  force  of  this  reasoning  cannot  be  denied,  it 
might  still  remain  possible  to  regard  diseases  as  occasion- 
ally favourable  to  human  evolution  in  an  indirect  way. 


Can  Disease  Favour  Evolution?        187 

Reference  will  perhaps  be  made  to  the  immunity  that  en- 
sues upon  many  of  the  infectious  diseases,  constituting  a 
protection  against  renewed  infection.  What  happens  in 
these  cases,  however,  is,  not  that  the  morbid  change  is  last- 
ingly retained  so  as  to  become  a  permanent  possession  of 
the  individual  and  his  offspring,  but  that,  after  complete 
cure,  a  modification  of  the  body  is  established  which  has 
no  disease-producing  significance  whatever,  but  exists  in 
association  with  a  condition  of  perfect  general  health. 
Does  the  change  promote  the  functional  capacity  of  the  in- 
dividual, and  therewith  favour  the  evolution  of  the  human 
race?  This  cannot  be  maintained  for  a  moment.  The 
functional  capacity  of  the  immune  individual  is  in  no  way 
superior  to  that  of  one  who  remains  liable  to  the  disease. 
As  regards  certain  diseases,  however,  a  further  argument 
is  possible.  In  the  case  of  tuberculosis,  for  example,  pre- 
disposition is  frequently  associated  with  general  bodily 
weakness.  It  may  be  contended  that  the  immune  individ- 
ual, who  is  more  vigorous  in  body,  is  endowed  with  greater 
functional  capacity.  This  is  perfectly  true;  but  if  the 
question  arises  whether  such  an  individual  represents  a 
better  evolved  form  of  human  being,  we  must  not  compare 
him  with  the  weakly  individuals  above  described.  We 
must  ask,  on  the  contrary,  whether  his  non-susceptibility 
has  per  se  raised  him  to  a  higher  level  of  functional  capac- 
ity, and  this  question  we  are  compelled  to  answer  in  the 
negative. 

It  is  perfectly  true,  as  regards  acquired  immunity,  that 
the  individuals  thus  distinguished  are  more  permanently 
valuable  for  the  evolution  of  the  human  race  than  those 
who  remain  susceptible  to  infection,  and  that  the  former 
are  therefore  of  higher  value  than  the  latter.  But  they 
do  not  on  this  account  constitute  a  higher  form  in  any 
genuine  sense,  and  their  immunity  would  be  altogether 
worthless  if  the  infectious  disease  did  not  exist. 

Reference  may  now  be  made  to  the  following  additional 
considerations.     When  entire  races,  or  the  inhabitants  of 


188  Heredity,  Disease  and  Human  Evolution 

entire  continents,  are  exposed  for  centuries  to  the  inci- 
dence of  an  infectious  disease,  they  acquire  in  consequence 
a  notable  diminution  of  susceptibility.  When  the  infec- 
tion recurs  they  suffer  less  than  those  who  are  exposed  for 
the  first  time  in  their  history.  Experience  shows  that 
the  infectious  diseases  of  childhood,  when  introduced  to 
islands  where  the  diseases  have  hitherto  been  unknown, 
prove  far  more  destructive  than  they  do  with  us. 

The  less  susceptible  peoples  therefore  suffer  less  than 
others,  and  if  the  former  happen  to  stand  at  a  higher  level 
of  civilisation  than  the  latter,  it  follows  that  the  more 
valuable  elements  of  the  race  will  be  better  preserved  than 
the  less  valuable.  But  what  is  the  importance  of  this 
when  compared  with  the  enormous  injuries  inflicted  by  the 
infectious  diseases  in  past  centuries,  and  to  be  inflicted 
by  them  in  the  future  notwithstanding  the  relative  im- 
munity of  the  peoples  among  whom  they  have  long  pre- 
vailed ?  It  would  obviously  be  much  better  if  these  diseases 
did  not  exist  at  all.  We  have  also  to  take  into  considera- 
tion, as  regards  races,  the  fact  to  which  allusion  was  made 
above  as  regards  individuals,  that  while  it  is  true  that  in 
the  case  of  the  comparatively  immune  peoples  the  losses 
inflicted  by  disease  are  less  severe,  their  immunity  does 
not  advance  them  to  a  higher  stage  of  evolution,  for  if  the 
diseases  in  question  had  not  existed,  they  would  not  merely 
stand  where  they  do  now,  but  would  unquestionably  occupy 
a  higher  level.  For  it  is  indubitable  that  diseases,  with 
their  manifold  injurious  consequences,  have  tended  to 
check  racial  evolution  as  a  whole. 

All  these  arguments  lead  to  the  conclusion  that  the  mor- 
bid states  affecting  our  bodies,  and  the  changes  that  re- 
main in  our  bodies  after  recovery  from  these  states,  may, 
indeed,  under  certain  conditions,  have  a  permanent  and 
valuable  effect,  but  that  they  are  in  no  way  adapted  to 
lead  to  the  development  of  any  new  qualities  favourable 
to  human  evolution. 

We  may  approach  the  question  in  another  way  if,  instead 


Can  Disease  Favour  Evolution?       189 

of  considering  the  conditions  of  our  own  time,  we  contem- 
plate those  of  the  whole  organic  world  throughout  the 
enormous  period  of  its  evolution,  and  ask  ourselves  what 
part  diseases  have  played  in  that  evolution,  and  what  part 
they  may  still  be  playing.  Starting  with  the  idea  that  bj^ 
a  change  in  vital  conditions  a  portion  of  the  individuals 
exposed  to  such  a  change  may  be  led  to  undergo  adapta- 
tion, that  is  to  say,  that  in  response  to  the  new  environ- 
mental influences  they  may  experience  certain  transfor- 
mations in  some  part  of  the  body  sufficient  to  constitute  a 
specific  differentiation,  whilst  other  members  of  the  same 
species,  proving  incompetent  to  adapt  themselves  to  the 
new  conditions,  may  consequently  perish,  we  may  main- 
tain that  in  such  a  case  disease  has  led  to  the  origin  of  a 
species.  For  those  individuals  that  perished  did  not  do 
so  without  reason;  their  deaths  were  due  to  pathological 
changes  which  appeared  in  their  bodies  in  consequence  of 
the  new  conditions  of  existence  which  to  them  proved  in- 
supportable— in  other  words,  they  succumbed  to  some  ill- 
ness. On  this  line  of  reasoning  it  might  be  maintained 
that  every  kind  of  illness  that  occurs  to-day  is  competent 
to  lead  to  the  appearance  of  new  specific  characteristics, 
and  in  this  way  to  favour  evolution  in  general.  But  it  is 
necessary  to  point  out  that  the  pathological  changes  did 
not  make  their  appearance  in  those  individuals  that  were 
able  to  undergo  adaptation,  but  in  the  others,  in  those 
who  succumbed  because  of  their  failure  to  undergo  adapta- 
tion, and  that  therefore  the  influence  of  the  pathological 
processes  in  promoting  evolution  was  extremely  indirect. 
They  operated  in  this  way  only,  that  the  inferior  elements 
disappeared  and  made  room  for  the  superior  ones.  Thus 
the  advance  of  the  latter  cannot  be  said  to  have  occurred 
as  a  direct  consequence  of  the  illnesses. 

We  must  further  remember  that  such  new  vital  condi- 
tions cannot  be  identified,  or  even  closely  compared,  with 
the  abnormal  influences  that  we  now  recognise  to  be  the 
exciting  causes  of  internal  disease.    In  the  general  course 


190  Heredity,  Disease  and  Human  Evolution 

of  evolution  it  was  changes  of  temperature,  climate,  damp- 
ness or  dryness  of  soil,  a  change  from  life  on  land  to  life 
in  the  water  or  the  reverse,  a  change  of  nutriment,  etc., 
which  led  to  the  origin  of  species,  but  never  the  action 
of  those  disease-producing  micro-organisms  which  play  so 
great  a  part  in  inducing  pathological  changes  to-day.  It 
is  true  that  in  earlier  stages  of  evolution  micro-organisms 
may  have  induced  disease,  but  they  cannot  have  led  to 
the  formation  of  new  species.  They  are  not  competent  to 
do  anything  of  the  kind,  and  this  first  of  all  because  they 
never  affect  all  the  individuals  of  a  species  simultaneously, 
as  influences  must  do  if  they  are  to  effect  a  selection  of 
individuals  competent  for  adaptation.  Further  they  take 
effect  suddenly,  intensely,  and  transiently,  injuring  living 
creatures  in  such  a  way  as  to  render  them  incompetent  to 
habituate  themselves  to  the  unfavourable  circumstances; 
and  moreover,  in  view  of  the  relatively  rapid  course  of 
the  diseases  in  question  there  is  no  time  for  such  adapta- 
tion to  take  place.  Adaptation  is  dependent  upon  a  long 
continued  and  gradual  transformation,  and  it  can  there- 
fore occur  only  when  the  changed  conditions  remain  in 
operation  without  intermission.  In  the  third  place,  it 
must  be  noted  that  reduced  susceptibility  to  infection,  as 
explained  above,  does  not  signify  the  constitution  of  a  new 
species,  and  it  is  all  the  more  impossible  to  accept  the  view 
that  acquirement  of  immunity  has  any  such  significance, 
inasmuch  as  we  do  not  know  of  a  single  case  in  which  a 
people  exposed  to  infection,  for  however  many  hundred 
years,^  has  acquired  complete  and  permanent  immunity. 
At  longer  or  shorter  intervals  epidemics  continue  to  ap- 
pear. 

We  conclude  that  diseases,  in  the  narrower  sense  of  the 
term,  have  never  been  determinative  factors  in  that  evo- 
lution of  the  organic  world  which  is  characterised  by  the 
formation  of  new  and  more  highly  organised  species.  If, 
moreover,  it  be  suggested  that  in  over-populated  areas  the 
infectious  diseases  may  cause  great  destruction  of  life,  and 


Can  Disease  Favour  Evolution?        191 

thereby  secure  for  the  survivors  better  conditions  of  ex- 
istence, we  must  draw  attention  to  the  fact  that  this  does 
not  per  se  involve  the  origination  of  a  better  type,  and 
further  that  the  disease  is  not  per  se  a  direct  cause  of  trans- 
formation in  the  individuals  that  do  not  succumb  to  it. 

From  whatever  side  we  look  at  the  question  we  are  al- 
ways led  to  the  same  conclusion  that  diseases  have  no  direct 
influence  upon  the  physical  evolution  of  the  organic  world 
in  general  or  of  the  human  race  in  particular,  and  that  at 
most  they  may  here  and  there  indirectly  lead  to  some 
trifling  advantage — an  advantage  that  is,  however,  quite 
inconsiderable  in  comparison  with  the  enormous  injury  in- 
flicted by  illness  on  our  race. 

Perhaps  the  question  may  be  asked  whether  it  is  really 
true  that  humanity  as  a  whole  suffers  injury  from  disease. 
If  we  put  aside  all  subjective  and  personal  considerations, 
and  remove  to  a  viewpoint  from  which  we  can  contem- 
plate the  human  race  as  a  whole,  in  its  past  and  future 
evolution,  shall  we  then  receive  the  impression  that  dis- 
eases interfere  with  the  forward  movement  of  mankind, 
and  shall  we  be  forced  to  conclude  that  man  would  have 
advanced  faster  in  the  past  and  would  advance  more  ef- 
fectively in  the  future  if  diseases  did  not  exist?  Let  us 
suppose  that  mankind  had  always  been  healthy,  and  would 
always  remain  healthy,  would  the  results  of  this  change 
be  purely  advantageous?  The  adverse  view  is  possible.  If 
there  were  no  such  thing  as  illness,  if  no  one  died  prema- 
turely, if  all  survived  to  old  age,  the  world  would  soon  be 
overcrowded,  unless  reproduction  were  retarded  to  an  ex- 
traordinary degree.  The  replacement  of  human  beings 
would  become  much  less  rapid,  and  a  rapid  replacement 
certainly  has  its  uses,  because  of  the  continued  occurrence 
of  new  dispositions  and  combinations  which  is  its  necessary 
result;  and  further  the  percentage  of  aged  people  would 
become  much  greater,  and  this  would  necessarily  involve 
a  diminution  in  the  general  functional  capacity.  Such 
arguments  as  these  may  lead  to  the  conclusion  that  the 


192  Heredity,  Disease  and  Human  Evolution 

endowment  of  our  race  with  perfect  health  would  not  be 
free  from  disadvantages,  and  the  attempt  might  therefore 
be  made  to  put  up  with  the  existence  of  diseases,  and  to 
make  the  best  of  them.  To  such  arguments  we  may  reply, 
first  that  mankind  would  certainly  learn  how  to  deal  with 
the  alleged  drawbacks,  which  are  purely  theoretical,  and 
secondly  that  in  any  case  these  drawbacks  would  be  far 
less  serious  than  are  the  injuries  to-day  actually  inflicted 
upon  mankind  by  disease.  The  condition  of  general  good 
health  would  certainly  be  preferable  even  if  it  were  found 
to  possess  a  seamy  side. 

These  considerations  apart,  such  a  view  of  illness  would 
never  give  practical  satisfaction.  We  desire  to  remain 
healthy,  and  we  feel  disease  to  be  something  of  a  dishar- 
monious nature,  of  which  we  wish  to  rid  ourselves.  Human 
beings  will  therefore  always  concentrate  their  attention 
upon  the  injuries  due  to  disease,  and  will  remain  indiffer- 
ent or  sceptical  as  to  the  benefits  which,  from  this  lofty 
standpoint,  are  alleged  to  accrue  from  illness.  Such  ideas 
as  those  we  have  discussed  will  not  help  men  to  agree  to 
put  up  with  disease.  The  individual  will  remain  com- 
pletely indifferent  to  the  possibility  that  the  abolition  of 
disease  might  involve  a  less  effective  evolution  of  the  human 
race. 

But  if  men  will  refuse,  on  the  basis  of  such  arguments, 
to  admit  that  illness  has  an  advantageous  side,  there  is 
yet  another  point  of  view  which  they  may  be  asked  to  con- 
sider. It  is  conceivable  that  pathological  states  are  useful 
to  our  race  in  another  way,  not  because  they  lead  directly 
or  indirectly  to  changes  in  bodily  organisation,  but  because 
they  spur  us  on  to  all  kinds  of  functional  activities  which 
promote  our  advance  in  civilisation,  functional  activities 
which  might  be  partially  or  wholly  neglected  if  disease 
did  not  exist. 

If  this  were  really  so,  disease  might  then  be  supposed  to 
work  for  good  in  one  way  or  another,  we  might  speak  of 
its  influence  in  this  or  in  that  direction — to  employ  a  word 


Can  Disease  Favour  Evolution'?        193 

often  misused — as  "purposive."  Before  we  proceed,  it  is 
necessary  to  study  the  precise  significance  of  this  term. 

When  we  speak  of  an  organ  as  having  a  purposive  char- 
acter we  express  the  opinion  that  this  organ  is  so  con- 
structed as  to  fulfil  in  the  best  possible  way  the  "purpose" 
for  which  it  exists.  What  do  we  mean  by  purpose,  and 
when  are  we  justified  in  using  the  word?  Only  when  we 
assume  that  to  effect  this  purpose  is  or  has  been  the  delib- 
erate intention  of  a  personality.  Purposes  cannot  exist 
unless  willed  by  some  intelligent  being.  This  idea  is  in- 
volved in  the  definition  of  the  term.  It  follows  that  only 
the  theist  is  justified  in  speaking  of  purposes  in  nature, 
only  one  who  conceives  that  when  God  created  the  world 
He  created  it  and  everything  it  contains  with  a  definite 
intention,  to  fulfil  definite  purposes,  and  that  he  adapted 
to  these  purposes  the  structure  of  living  organisms. 

One,  however,  who  regards  the  universe  not  as  created, 
but  simply  as  a  datum  of  experience,  cannot  and  must  not 
speak  of  purposes,  or  is  justified  in  doing  so  only  in  so 
far  as  living  beings  deliberately  devote  themselves  to  the 
attainment  of  consciously  foreseen  ends — a  faculty  almost 
peculiar  to  mankind.  Yet  even  those  who  do  not  regard 
the  world  as  created  are  often  inclined  to  speak  of  pur- 
poses in  a  more  general  sense.  They  say,  indeed,  that  the 
ordinary  crude  teleology  is  far  from  their  minds,  and  that 
all  they  have  in  view  are  immanent  purposes.  What  sort  of 
marvels  are  these?  Immanent  purposes  are  purposes  con- 
tained within  the  things  that  are  purposed.  But  as  "pur- 
poses" they  can  be  contained  within  these  things  ,(it  is 
necessary  to  insist  upon  this  again)  only  if  at  the  time 
the  things  were  created  the  purposes  were  introduced  by 
a  reflective  personality — by  God,  If  we  do  not  mean  to 
imply  this,  if  the  purposes  are  inseparately  associated  with 
the  things,  if  they  have  always  been  there,  if  they  are  im- 
manent, we  are  using  the  word  purpose  in  a  sense  that 
cannot  properly  attach  to  it. 

The  universe  evolves  in  accordance  with  certain  self- 


194  Heredity,  Disease  and  Human  Evolution 

contained  rules.  Each  antecedant  process  leads  to  a  con- 
sequent, the  latter  is  regarded  as  the  "purpose"  of  the 
former ;  and  because  the  first  conditions  the  second  the  first 
is  spoken  of  as  "purposive"  in  relation  to  the  second. 
Or  an  organ,  such  as  the  eye,  is  adapted  by  its  structure 
for  vision,  and  we  are  told  that  the  eye  exists  for  the 
purpose  of  fulfilling  this  function.  Those  v^ho  use  such 
language  fail  to  take  into  consideration  that  inasmuch  as 
the  second  process  is  dependent  upon  the  first,  the  first 
process  must  necessarily  be  adapted  to  produce  this  par- 
ticular end,  for  were  it  otherwise  the  second  process  could 
not  possibly  occur;  and  they  fail  to  recognise  that  the 
eye  is  necessarily  apt  for  seeing,  for  otherwise  it  would 
not  be  an  eye  at  all.  It  is,  therefore,  a  matter  of  course 
that  a  thing  is  "purposive"  for  that  which  it  causes  or 
for  the  function  which  it  performs.  It  follows  that  the 
concept  purposive,  when  used  by  a  scientific  thinker,  has 
really  no  meaning  at  all,  is  a  purely  descriptive  and  there- 
fore superfluous  term,  means  nothing  more  than  would  be 
equally  well  expressed  by  the  words  "capable-of -existing." 
Only  the  theist  is  justified  in  maintaining  that  vision  is 
the  purpose  for  which  the  eye  exists,  and  that  the  eye 
is  purposive  to  this  intent ;  all  that  the  non-theist  may  say 
is  that  the  eye  possesses  the  function  of  vision  because  it 
has  evolved  in  this  way. 

The  employment  of  the  word  purposive  by  the  non- 
theist  is  not  merely  superfluous  but  is  open  to  serious  ob- 
jection, for  it  impairs  the  consistency  of  his  attitude,  and 
leads  people  to  believe  that  he  has  not  freed  himself  from 
theistic  conceptions. 

If  it  be  improper  to  employ  the  term  purposive,  it  is  no 
less  incorrect  to  speak  of  things  as  being  "unpurposive. " 
It  is  obvious  that  the  theist  has  no  right  to  use  such  an 
expression.  It  is  inconceivable  that  God  should  have  set 
himself  purposes  to  fulfil  and  at  the  same  time  have  cre- 
ated something  inconsistent  with  those  purposes.  What  ap- 
pears unpurposive  to  man  has  some  purpose  from  God's 


N 


Can  Disease  Favour  Evolution?        195 

point  of  view,  although  the  nature  of  this  purpose  is  be- 
yond man's  understanding.  The  theist  is  forced  to  regard 
diseases  as  in  some  way  adapted  to  fulfil  God's  purposes. 
For  the  theist,  therefore,  nothing  in  the  universe  can  be 
unpurposive,  for  he  must  regard  everything  that  exists  as 
purposive  in  the  sight  of  God.  He  has  no  right  to  intro- 
duce his  trivial  subjective  considerations  into  God's  crea- 
tion! 

The  man  of  science,  however,  has  no  better  justification 
than  the  theist  for  using  the  term  "unpurposive."  What- 
ever exists  has  come  into  existence  in  accordance  with  evo- 
lutionary needs.  Consider,  for  example,  the  case  of  the 
vertical  organs  of  which  we  hear  so  much  to-day.  If  these 
organs  are  no  longer  functional,  in  relation  to  this  func- 
tionless  condition  (which  to  the  theist  must  seem  a  part  of 
God's  purposes)  the  atrophy  of  the  organ  must  be  regarded 
as  just  as  "purposive"  as  the  existence  of  the  eye  must  be 
regarded  as  "purposive"  in  relation  to  the  function  of 
vision.  If  diseases  lead  to  death,  they  too  are  "purposive" 
in  relation  to  this  unavoidable  natural  event. 

If  in  the  course  of  our  exposition  we  wish  to  make  use 
of  the  current  terminology,  we  shall  find  it  impossible  to 
distinguish  between  purposive  and  unpurposive.  Every- 
thing that  exists  is  ' '  purposive. ' '  We  see  this  at  once  when 
we  attain  to  the  right  outlook,  and  are  careful  to  avoid 
being  biased  by  man's  subjective  impressions. 

The  scientific  thinker  should,  however,  avoid  using  the 
expression  purposive.  He  must  speak  objectively,  and  he 
fails  to  do  so  when  he  speaks  of  purpose,  for  when  he 
does  this  he  subordinates  the  universe  to  his  own  sub- 
jective impressions,  considering  not  what  actually  is  but 
what  he  conceives  in  imagination.  This  is  not,  indeed,  his 
intention.  When  he  uses  the  word  purposive  all  he  means 
to  imply  is  that  the  consequent  follows  the  antecedent  in 
accordance  with  law,  that  the  structure  of  an  organ  pre- 
cisely corresponds  with  its  function.  He  knows,  moreover, 
that  this  function  has  come  into  existence  through  adapta- 


196  Heredity,  Disease  and  Human  Evolution 

tion  to  external  conditions.  Why,  then,  does  he  say  "pur- 
posive" instead  of  ''adapted"?  The  latter  expression  is 
admirably  objective,  meets  all  the  needs  of  the  case,  and 
cannot  possibly  be  misinterpreted.  The  eye  is  adapted  to 
vision,  the  v^ing  to  flight,  the  lung  to  breathing,  every 
organ  to  its  function. 

Another  brief  explanation  is  still  requisite.  We  said 
above  that  man  exhibits  purpose,  that  he  deliberately  de- 
votes himself  to  the  attainment  of  consciously  foreseen 
ends.  It  may  be  asked,  however,  how  he  can  do  this,  if 
in  the  world-all  no  purposes  exist.  Since  man  is  a  portion 
of  the  universe,  purposes  must  exist  also  in  the  universe, 
or  they  could  not  exist  in  man.  His  pursuit  of  deliberate 
aims  is  merely  the  expression  of  his  imperfection,  of  his 
feeling  that  he  lacks  much,  of  his  yearning  to  provide 
what  is  lacking.  Hence  he  purposes.  But  in  the  world-all, 
which  is  all-embracing,  which  lacks  nothing  because  noth- 
ing exists  outside  it,  there  are  no  purposes,  there  is  only 
a  developmental  process,  a  continuous  transformation  pro- 
ceeding in  accordance  with  law,  without  beginning  and 
without  end,  wherein  every  process  is  adapted  to  that  which 
has  gone  before,  to  that  which  is  simultaneous,  and  to 
that  which  follows. 

From  this  evolution  of  the  world-all  man's  purposiveness 
can  be  deduced  in  yet  another  way.  As  a  part  of  the  whole, 
man  finds  himself  introduced  into  the  evolutionary  proc- 
ess; he  knows  that  he  does  not  remain  as  he  is,  but  con- 
tinues to  undergo  transformation.  He  is  aware  that  his 
present  constitution  contains  the  conditions  of  that  which 
is  to  come,  for  such  is  the  nature  of  evolution.  To  him, 
therefore,  the  future  becomes  an  end,  a  goal  towards  which 
he  strives,  and  it  seems  to  him  to  be  the  purpose  of  his 
life  to  attain  to  this  goal.  He  is  thus  led  to  deduce  the 
idea  of  purpose  from  the  evolutionary  process  that  is  pro- 
ceeding in  himself  and  in  the  world-all.  And  just  as  he 
erroneously  feels  his  own  evolution,  which  proceeds  solely 
in  accordance  with  law  and  which  follows  a  necessary 


Can  Disease  Favour  Evolution?        197 

course,  to  be  purposive,  "because  it  is  conducting  him 
towards  the  goal  which  he  desires  to  attain,  so  also  he 
erroneously  introduces  the  idea  of  purpose  into  the  gen- 
eral evolution  of  the  world-all. 

Returning  from  this  digression  concerning  the  purposive 
to  consider  the  question  whether  diseases  play  a  part  in  the 
evolutionary  process  of  our  race,  are  adapted  to  that  proc- 
ess to  this  extent,  that  they  spur  man  on  to  functional 
activities  which  perhaps  he  would  not  "have  undertaken  in 
like  manner  in  the  absence  of  this  stimulus,  we  shall  pro- 
ceed to  discuss  the  matter  in  connexion  with  the  principal 
human  activities. 

We  think  first  of  mental  disorders.  Unquestionably  the 
existence  of  these  has  contributed  to  our  understanding 
of  the  conditions  of  mental  life.  As  concerns  mental  dis- 
orders which  lead  to  infraction  of  the  law,  the  discussions 
as  to  criminal  responsibility  and  liability  to  punishment 
in  the  case  of  the  insane  have  led  to  a  vigorous  investiga- 
tion of  the  problem  of  the  freedom  of  the  will  (See  p.  46), 
and  have  certainly  contributed  to  its  solution.  The  same 
discussions  have  also  exercised  a  favourable  influence  upon 
legislation,  but  this  has  not  really  involved  any  advantage 
to  the  race,  for  no  significance  can  be  attached  to  this 
legislative  change  when  considered  by  itself.  For  if  there 
were  no  persons  suffering  from  mental  disorder,  there 
would  be  no  need  of  the  particular  legal  reforms  which 
are  instituted  solely  on  their  account.  As  regards  the 
advantages  accruing  from  a  better  understanding  of  the 
problem  of  free  will,  these  are  far  more  than  outweighed 
by  the  enormous  damage  entailed  by  mental  disorders  upon 
the  sufferers  themselves  and  their  associates.  Besides, 
whatever  assistance  we  may  have  gained  in  the  under- 
standing of  mental  processes  from  the  study  of  mental  dis- 
order, we  should  have  arrived  at  the  same  end,  though  per- 
haps somewhat  more  slowly,  by  other  means. 

There  is  another  way  in  which  disease  may  be  regarded 
as  of  importance  in  relation  to  the  mental  life.     It  is  a 


198  Heredity,  Disease  and  Human  Evolution 

familiar  statement  that  genius  and  mental  disorder  are 
very  intimately  related.  In  a  certain  sense  this  is  not 
difficult  to  understand.  The  extremely  one-sided  develop- 
ment of  particular  tendencies  characteristic  of  genius  is 
likely  to  be  associated  with  an  abnormal  development  of 
other  sides  of  the  mental  life.  If  it  were  true  that  genius 
could  not  exist  except  in  association  with  such  a  defective 
and  pathological  side  of  the  mind,  if  the  existence  of  the 
pathological  side  were  an  indispensable  condition  of  the 
high  development  of  the  normal  side  characteristic  of 
genius,  a  disease  would  in  fact  render  possible  the  high- 
est attainable  development  of  the  mental  faculties,  and 
would  thus  be  useful  to  mankind.  First  of  all,  however, 
genius  is  not  found  solely  in  association  with  disease.  Sec- 
ondly, we  should  certainly  not  be  prepared  to  pay  for  the 
highest  possible  mental  capacity  by  the  acceptance  of  all 
diseases;  we  should  prefer  to  do  without  a  certain  propor- 
tion of  persons  of  genius,  if  thereby  we  could  make  all 
other  human  beings  healthy. 

It  may  further  be  suggested  that  the  existence  of  disease 
has  been  favourable  in  many  ways  to  our  researches  in  the 
domain  of  natural  science.  For  example,  the  search  for 
medicaments  has  led  us  to  acquire  a  much  more  precise 
knowledge  of  many  plants  than  we  should  otherwise  pre- 
sumably have  gained,  and  in  this  way  great  advantage 
has  certainly  accrued  to  scientific  botany. 

Similar  considerations  apply,  though  to  a  far  less  extent, 
to  the  manner  in  which  our  study  of  the  animal  world 
has  been  favoured  by  the  existence  of  disease. 

Above  all,  our  knowledge  of  vegetable  and  animal  or- 
ganisms has  been  enormously  enriched  because  many  of 
these  organisms  are  exciting  causes  of  disease,  and  because 
we  have  therefore  been  led  to  undertake  far  more  thorough 
investigations  than  we  should  have  undertaken  had  this 
particular  reason  not  existed.  The  knowledge  thus  ac- 
quired within  the  domain  of  disease  has  proved  of  so 
much  significance  outside  that  domain  in  promoting  our 


Can  Disease  Favour  Evolution?        199 

understanding  of  the  general  processes  of  life,  that  our 
knowledge  of  allied,  but  non-pathogenic  organisms  has  been 
greatly  increased.  Thus  the  interest  aroused  in  micro-or- 
ganisms as  the  exciting  causes  of  disease  has  stimulated 
the  study  of  micro-organisms  in  general,  and  in  like  man- 
ner our  interest  in  the  malarial  piirasites  has  led  us  to 
make  a  more  comprehensive  study  of  all  the  protozoa. 

Our  efforts  towards  the  cure  of  disease  have  also  had  a 
favourable  reaction  upon  biological  research.  Since  many 
tissues  are  destroyed  by  pathological  processes,  it  became 
desirable  to  understand  in  what  manner  the  destroyed  ele- 
ments could  be  replaced.  This  was  the  starting  point  of 
comprehensive  researches  into  the  process  of  regeneration. 
It  is  true  that,  long  before,  the  problem  had  been  attacked 
on  purely  scientific  grounds,  but  in  the  interest  of  thera- 
peutics far  more  vigorous  efforts  were  subsequently  made 
in  this  field.  In  the  same  connexion  the  study  of  the 
so-called  compensatory  hypertrophy  and  that  of  functional 
adaptation  received  a  considerable  impetus. 

Further,  the  vital  processes  of  the  normal  body  have  had 
much  light  thrown  upon  them  in  consequence  of  the  studj^ 
of  pathological  processes,  and  our  knowledge  of  the  normal 
tissues  has  in  many  fields  been  promoted  by  a  study  of 
morbid  changes,  and  has  advanced  far  more  rapidly  than 
would  otherwise  have  been  the  case. 

Chemistry,  too,  has  to  thank  medicine  for  much  assist- 
ance, especially  in  connexion  with  the  study  of  medicinal 
remedies.  ]\Iany  new  substances  have  been  produced  which 
would  almost  certainly  have  remained  unknown  but  for 
the  existence  of  the  diseases  for  the  cure  of  which  these 
substances  have  been  artificially  manufactured.  In  this 
way  theoretical  chemistry  has  gained  much  benefit.  No 
less  advantage  has  been  derived  from  a  study  of  patho- 
logic-chemical processes  in  the  diseased  body. 

We  must  not  forget  that  the  physic/il  sciences  have  de- 
rived profit  from  the  same  source.  The  applications  of 
electricity,  of  Rontgen  rays  and  of  radium,  to  the  treat- 


200  Heredity,  Disease  and  Human  Evolution 

ment  of  disease,  have  involved  the  acquirement  of  knowl- 
edge which  has  not  been  without  influence  in  the  domain 
of  physics. 

It  is,  in  fact,  impossible  to  deny  that  pathology  has  fur- 
nished a  considerable  stimulus  to  the  progress  of  the  natu- 
ral sciences.  But  are  the  advantages  so  great  that  we 
should  be  willing  on  their  account  to  pay  the  price  in- 
volved in  the  acceptance  of  disease?  Assuredly  not.  "We 
would  gladly  give  up  the  comparatively  slight  advantages 
which  have  accrued  to  science  from  the  domain  of  path- 
ology, if  in  exchange  we  could  secure  the  benefits  of  per- 
manent health.  The  injuries  inflicted  by  diseases  are  so 
enormous  that  the  advantages  just  enumerated  hardly 
count  in  the  other  scale.  Besides,  there  are  no  gains  to 
science  dependent  upon  the  existence  of  disease  which 
would  not  ultimately  have  been  acquired  in  other  ways. 

Again,  diseases  have  led  to  many  improvements  in  social 
conditions.  When  people  came  to  understand  that  the  dif- 
fusion of  certain  diseases  was  greatly  favoured  by  defective 
hygiene  and  bad  housing  conditions,  improvement  was  de- 
manded in  the  general  interest.  It  came  to  be  regarded  as 
a  matter  of  great  importance  to  improve  the  external  condi- 
tions of  life,  to  secure  a  good  water-supply,  to  provide 
sound  and  uncontaminated  food,  to  attend  to  drainage  and 
sewage,  and  (although  still  very  inadequately)  to  see  to 
the  provision  of  better  habitations.  Yet  it  is  certainly 
open  to  question  whether  all  these  things  might  not  have 
been  done  even  sooner  had  disease  never  existed.  Beyond 
question,  healthy  human  beings  would  speedily  have 
thought  of  improving  the  conditions  of  existence,  nor  would 
the  means  have  been  lacking,  if  no  more  had  been  devoted 
to  the  purpose  than  the  sums  now  expended  in  the  struggle 
with  disease. 

"We  may  finally  consider  such  institutions  for  the  pro- 
motion of  general  welfare  as  the  system  of  national  insur- 
ance against  individual  pecuniary  loss  through  sickness  and 
the  national  provision  of  medical  treatment.    But  these  in- 


Can  Disease  Favour  Evolution?        201 

stitutions  are  created  expressly  to  deal  with  the  results 
of  disease,  and  would  be  altogether  superfluous  if  disease 
did  not  exist. 

We  see,  therefore,  that  the  advantages  alleged  to  accrue 
to  scientific  research  and  to  practical  life  in  consequence 
of  the  influences  of  disease  are  insignificant  in  comparison 
with  the  colossal  injuries  which  disease  causes;  that  many 
of  them  would  have  been  attained  without  this  particular 
stimulus;  and  that  others  would  be  superfluous  in  the  ab- 
sence of  disease.  The  advantages  in  question  will,  there- 
fore, not  lead  us  to  slacken  our  efforts  to  do  all  that  is 
possible  to  secure  health  for  the  human  race. 


CHAPTER  VIII 

DISEASE  AND  RELIGION 

In  the  previous  chapters  we  have  adduced  sufficient  evi- 
dence to  show  that  diseases  inflict  an  enormous  amount  of 
damage  upon  the  individual,  the  family,  the  nation,  and 
posterity,  and  that  they  entail  no  compensating  advantages 
worth  mentioning.  It  is  true  in  the  account  just  given  of 
the  relationships  between  disease  and  the  future  bodily 
and  mental  development  of  the  human  race,  between  dis- 
ease and  the  individual  sciences,  and  between  disease  and 
social  problems,  we  have  seen  that,  occasionally  and  within 
narrow  limits,  diseases  may  exercise  a  stimulating  and 
progressive  influence;  but  we  have  also  learned  that  the 
losses  greatly  exceed  the  gains.  We  have,  however,  not  yet 
discussed  the  extremely  important  relationship  of  diseases 
to  religious  views.  It  was  impossible  to  consider  this  mat- 
ter adequately  within  the  limits  of  the  foregoing  chapter, 
and  we  propose  to  devote  the  present  chapter  to  an  inde- 
pendent and  thorough  examination  of  the  question. 

If  there  is  one  thing  more  than  all  others  likely  to  turn 
man's  thoughts  towards  the  problem  of  the  meaning  of  his 
existence  and  the  nature  of  his  relationship  to  the  uni- 
verse, it  is  the  fact  that  disease  so  often  puts  a  premature 
term  to  his  career  and  so  frequently  inflicts  upon  him  se- 
vere suffering.  "We  might  even  regard  this  direction  of 
human  speculation  as  the  most  important  service  we  owe 
to  disease.  If  it  be,  indeed,  one  of  man's  chief  duties  to 
gain  a  clear  understanding  as  to  his  position  in  the  uni- 
verse, and  if  the  existence  of  disease  lead  him  to  attack 
this  problem  seriously  and  to  solve  it  wherever  possible, 
undoubtedly  great  benefit  must  be  derived.    We  have,  then, 

202 


Disease  and  Religion  203 

to  ask  whether  diseases  are  really  indispensable  to  induce 
men  to  occupy  themselves  with  such  problems,  and  whether 
a  consideration  of  diseases  is  likely  to  lead  us  to  a  dear 
understanding  of  the  matter.  Would  not  the  healthy  hu- 
man being  also  devote  his  attention  to  the  problem?  Un- 
questionably he  would.  The  infinite  complexity  of  nature 
is  ever  imposing  new  riddles,  and  urging  us  to  attempt 
their  solution.  By  a  profound  inner  impulse,  man  strives 
towards  knowledge ;  this  impulse  is  inborn ;  it  is  one  we 
cannot  but  obey.  Nor  can  it  be  doubted  for  a  moment 
that  the  healthy  individual  is  far  better  fitted  for  the 
acquirement  of  knowledge  than  the  invalid,  whose  atten- 
tion is  claimed  by  his  own  condition,  who  thinks  exclusively 
of  his  own  personal  interest,  who  is  indifferent  to  the  outer 
world  except  in  so  far  as  this  bears  upon  his  illness,  whose 
mental  functions  are  confused  or  one-sided  or  are  affected 
and  restricted  through  bodily  suffering.  It  is  obvious  that 
the  sick  man  will  be  less  successful  in  the  pursuit  of  knowl- 
edge than  the  healthy  one,  for  the  former,  especially  in  the 
case  of  mental  disorder,  is  really  incapable  of  contributing 
anything  of  value  towards  the  solution  of  such  problems. 
His  abnormal  state  imposes  every  kind  of  hindrance  and 
leads  him  to  false  conclusions.  Anything  which  one  who 
is  not  completely  normal  in  his  mental  life,  anything  which 
a  person  who  is  markedly  onesided  in  the  sense  explained 
early  in  this  book,  believes  himself  to  have  discovered,  must 
be  accepted  with  extreme  caution.  Of  what  use  is  it  that 
disease  should  furnish  a  stimulus  towards  the  solution  of 
the  problem  of  existence,  however  great  this  stimulus  may 
be,  if  by  the  very  fact  that  he  is  diseased  the  invalid  is 
deprived  of  the  capacity  for  attaining  to  a  satisfactory  un- 
derstanding of  these  problems?  The  invalid's  conclusions 
may  be  satisfactory  to  his  own  mind,  but  they  are  mean- 
ingless as  regards  the  general  advance  of  our  race,  and 
will  often  lead  astray.  Only  the  healthy  man,  the  logical 
thinker  who  gives  due  weight  to  all  relevant  considerations, 
can  count  upon  attaining  to  satisfactory  conclusions. 


204  Heredity,  Disease  and  Human  Evolution 

The  matter  may,  however,  he  approached  from  another 
point  of  view.  Even  if  it  be  true  that  as  far  as  invalids 
themselves  are  concerned  the  effects  of  the  diseases  from 
which  they  suffer  are  purely  disadvantageous,  if  their  ill- 
ness serve  only  to  prevent  the  attainment  of  a  solution  of 
the  very  problems  which  that  illness  leads  the  invalids  to 
propound,  it  may  still  remain  true  that  the  occurrence  of 
disease  leads  healthy  individuals  to  devote  more  attention 
to  the  problems  of  existence  than  would  otherwise  be  the 
case.  This  is  actually  so.  By  the  suffering  and  prema- 
ture death  of  his  fellow's  the  healthy  individual  is  urged 
in  the  suggested  direction,  and  we  cannot  deny  that  the 
impulse  towards  knowledge  is  thereby  strengthened,  and 
that  the  acquirement  of  valuable  results  may  be  accelerated 
in  consequence.  Before,  however,  agreeing  to  see  therein 
an  important  beneficial  result  of  disease,  we  must  consider 
two  objections.  First  of  all,  the  healthy  individual's  judg- 
ment will  be  less  independent  than  might  be  supposed.  His 
judgment  will  be  more  or  less  obscured  by  sympathy,  by 
his  participation  in  the  other's  suffering.  Secondly  we 
have  to  ask  whether  we  should  be  willing,  in  view  of  the 
benefits  under  consideration,  merely  in  order  to  obtain  a 
better  insight  into  the  relationships  of  things,  or  rather 
merely  in  order  to  have  our  attention  more  keenly  directed 
to  these  relationships,  to  accept  all  the  misery  and  distress 
resulting  from  disease.  It  cannot  be  doubted  that  we 
should  refuse  any  such  bargain.  The  profits  bear  no  reason- 
able comparison  with  the  losses.  Nor  must  we  forget  that 
in  consequence  of  the  diseased  or  abnormal  condition  of 
the  majority  of  human  beings  an  immeasurable  quantity 
of  mental  faculty  runs  to  waste.  Among  all  these  invalids 
there  must  be  many  who,  had  they  been  healthy,  would 
have  been  competent  for  far  more  extensive  mental  col- 
laboration, and  in  this  way  would  have  contributed  to 
human  advance  to  a  degree  far  greater  than  that  which 
corresponds  to  the  advance  now  effected  by  the  mental  la- 
bours of  healthy  individuals  in  consequence  of  the  stimulus 


Disease  and  Religion  205 

which  these  experience  owing  to  the  existence  of  disease. 
We  may  definitely  assert  that  had  human  beings  always 
been  healthy  we  should  be  further  advanced  than  we  are 
at  present  in  our  understanding  of  the  nature  of  things. 
Perfectly  elear  reflection,  neither  restricted  nor  enfeebled 
by  any  pathological  manifestations,  would  certainly  have 
brought  us  beyond  our  present  stage  of  knowledge.  Many 
wrong  turnings  would  have  been  avoided. 

For  example,  there  can  be  no  doubt  that  diseases  have 
had  a  great  influence  in  the  origination  of  the  pessimistic 
view  of  life,  above  all  because  illness  is  apparent  on  all 
hands,  and  seems  inseparably  associated  with  the  existence 
of  living  organisms.  How  can  a  world  be  good  which  is 
thus  permeated  by  disease?  Human  beings  apart,  we  see 
everywhere  conditions  which  with  more  or  less  justifica- 
tion (a  matter  to  be  discussed  in  the  concluding  chapter) 
are  regarded  as  pathological,  such  as  the  permanent  de- 
struction of  enormous  numbers  of  undeveloped  living  be- 
ings. But  human  pathology  is  here  chiefly  determinative, 
for  it  is  this  that  especially  forces  itself  upon  our  atten- 
tion. Disease  is  regarded  as  inseparable  from  human  ex- 
istence, as  from  the  existence  of  the  entire  organic  world, 
and  this  leads  to  pessimism.  But  are  we  really  justified 
in  considering  disease  as  an  essential  characteristic  of  the 
human  race  ?  Can  we  not  conceive  of  disease  as  non-exist- 
ent, without  man's  thereby  being  deprived  of  anything 
that  truly  goes  to  make  him  man?  We  can  certainly  do 
this.  We  can  very  well  imagine  that  all  human  beings 
might  be  healthy,  and  we  may  actually  hope  that  in  the 
future  the  prevalence  of  disease  will  continually  diminish. 
In  these  circumstances,  are  we  justified  in  allowing  the 
existence  of  disease  to  exercise  a  decisive  influence  upon 
our  general  view  of  the  universe?  Would  it  not  be  more 
correct  to  base  our  judgment  solely  upon  the  contemplation 
of  health,  and  to  deduce  therefrom  an  optimistic  view  of 
the  universe? 

It  is  not  merely  the  objective  contemplation  of  disease 


206  Heredity,  Disease  and  Human  Evolution 

which  has  led  to  pessimism.  Subjective  considerations  also 
exercise  an  influence  in  this  direction.  A  man's  own  mor- 
bid state  will  affect  his  views,  and  will  often  give  these  a 
pessimistic  tinge.  To  induce  this  it  is  not  necessary  that 
there  should  be  an  illness  causing  bodily  suffering,  nor 
yet  that  there  should  have  occurred  a  one-sided  mental 
development,  for  the  mere  possession  of  a  high  degree  of 
sensibility,  leading  its  possessor  to  overestimate  the  im- 
portance of  his  own  minor  troubles  and  those  of  others, 
will  lead  to  pessimism.  There  may  also  exist  in  certain 
human  beings  an  inborn  temperamental  tendency  which 
leads  them  to  see  everything  in  gloomy  colours.  In  con- 
tradistinction with  such  persons,  the  perfectly  healthy  man 
is  quite  free  from  any  inclination  to  pessimism  (and  the 
same  is  often  true  of  those  who,  though  physically  ill,  are 
mentally  normal).  Even  if  on  occasions  healthy  humanity 
may  feel  somewhat  gloomy  because  illnesses  continue  to 
exist,  still  the  natural  inclination  will  always  be  to  take 
an  optimistic  view  of  life.  The  world  is  full  of  unending 
beauties,  and  in  the  absence  of  any  morbid  disturbance  this 
must  necessarily  lead  to  optimism. 

Even  in  this  age  in  which  diseases  exist,  the  reflective 
human  being  cannot  take  other  than  an  optimistic  view. 
That  which  arises  from  disease  cannot  be  normal,  and  has 
therefore  no  right  to  influence  our  general  attitude  towards 
life.  Disease  is  produced  by  disease,  and  pessimism  is 
therefore  morbid. 

It  is  sometimes  contended  that  we  cannot  escape  from 
pessimism  because  diseases  are  a  necessary  appurtenance 
of  humanity.  It  is  true,  we  are  told,  that  we  can  conceive 
diseases  as  non-existent,  but  in  actual  fact  we  cannot  sep- 
arate them  from  the  general  evolutionary  process,  we  have 
to  take  them  into  account,  and  thus  we  are  constrained 
towards  pessimism.  But  this  merely  involves  an  admis- 
sion which  no  one  proposes  to  dispute  that  the  existence 
of  disease  is  mainly  responsible  for  the  origination  of  the 
pessimistic  view  of  life.    This  brings  us  back  to  our  start- 


Disease  and  Religion  207 

ing  point.  But  it  is  wrong  to  regard  disease  as  an  in- 
evitable and  integi'al  accessory  of  life.  In  the  case  of 
human  beings,  disease  is  certainly  not  necessary,  for  many 
diseases  are  obviously  preventible.  This  point  will  be 
considered  later. 

Let  us  now  proceed  with  our  discussion  of  the  signifi- 
cance of  diseases  in  relation  to  the  solution  of  the  problems 
of  existence.  Just  now  we  were  forced  to  the  conclusion 
that  as  far  as  concerns  our  understanding  of  man's  place 
in  the  universe,  disease  does  more  harm  than  is  compen- 
sated by  any  good  that  may  ensue  from  the  stimulus  to 
scientific  research  afforded  by  its  existence.  But  there  is 
another  aspect  in  which  the  significance  of  disease  may 
be  regarded  as  more  considerable,  for  its  existence  furnishes 
a  far  more  powerful  stimulus  to  the  emotional  than  it  does 
to  the  intellectual  side  of  our  nature — taking  the  term 
emotional  in  its  most  comprehensive  sense  to  include  our 
religious  views  of  life.  Through  disease,  the  question  of 
the  personal  relationship  of  the  individual  to  the  world-all, 
the  problem  of  human  destiny,  is  forced  to  the  front.  This 
may  be  supposed  to  involve  a  notable  advantage.  It  may 
be  contended  that  the  indifference  displayed  by  many  per- 
sons towards  religious  problems,  and  their  deliberate  avoid- 
ance of  the  consideration  of  such  questions,  are  deplor- 
able. But  this  attitude  would  be  gi'eatly  accentuated  were 
it  not  that  through  illness  people  are  often  rudely  com- 
pelled to  pay  attention  to  these  problems,  forced  to  give 
them  respectful  consideration,  and  this,  we  are  assured,  is 
a  benefit  we  owe  to  disease,  one  which  even  the  scientific 
thinker  cannot  fail  to  recognise.  For  men  of  science  can- 
not escape  the  problems  of  religion.  One  who  has  not 
thought  them  out,  one  who  has  failed  to  come  to  terms 
with  their  difficulties,  can  never  find  secure  standing 
ground.  He  must  settle  his  account  with  religion.  Among 
those  who  ultimately  find  complete  satisfaction  through  ex- 
clusive absorption  in  the  domain  of  scientific  ideas,  there  is 
certainly  no  one  but  has  felt  the  need  to  touch  upon 


208  Heredity,  Disease  and  Human  Evolution 

the  religious  sphere  (alwaj^s  understanding  the  term  re- 
ligion in  its  widest  possible  signification)  and  to  become 
clear  as  to  his  own  attitude  towards  religious  problems. 

By  these  considerations  we  are  led  to  recognise  that  dis- 
eases tend  to  turn  men's  minds  to  the  problems  of  religion. 
For  this  reason,  perhaps,  many  will  have  endeavoured  to 
put  up  with  the  existence  of  illness,  and  to  believe  that 
it  entails  more  benefit  than  disadvantage.  But  such  a  view 
would  be  justified  only  if  we  were  compelled  to  assume 
that  if  there  were  no  such  thing  as  disease  men  would 
not  concern  themselves  about  religious  problems.  We  can- 
not for  a  moment  accept  such  a  view.  On  the  contrary, 
it  is  beyond  question  that  even  if  human  beings  were 
perfectly  healthy  they  would  none  the  less  state  religious 
problems  and  do  their  best  to  solve  them.  The  stimulus 
furnished  by  the  existence  of  disease  is  superfluous. 

In  the  second  place,  it  must  not  be  forgotten  that  a 
healthy  humanity  would  find  a  much  more  satisfying 
answer  to  this  question  than  is  possible  to  our  race  when 
afflicted  as  now  by  disease.  It  is  obvious  that  in  religious 
matters,  as  in  others,  a  healthy  human  being  feels  and 
judges  more  accurately  than  a  diseased,  or  than  one  who 
is  influenced  and  confused  in  consequence  of  the  illness 
of  others.  Trouble  and  anxiety  such  as  are  caused  by 
illness  and  premature  death  necessarily  cloud  the  judg- 
ment, and  in  this  way  the  advantage  ascribed  to  illness, 
because  it  turns  our  .thoughts  to  religious  questions,  is 
counterbalanced,  and  indeed  enormously  outweighed,  by 
the  disadvantages  that  ensue  from  the  great  limitations 
imposed  thereby  upon  our  rational  faculties.  It  follows 
that  for  the  solution  of  these  problems  the  general  effect  of 
illness  is  simply  injurious. 

Yet  there  can  be  no  doubt  that  disease  is  to-day  responsi- 
ble for  the  intensity  with  which  most  people  devote  them- 
selves to  religious  questions.  Illness  and  premature  death 
continually  recall  the  thoughts  to  the  problem  of  human 
destiny. 


Disease  and  Religion  209 

When  we  see  that  most  persons  die  an  unnatural  death, 
when  so  many  succumb  before  the  onset  of  old  age,  often 
long  before,  and  frequently  in  early  childhood,  when  many 
suffer  from  illnesses  of  a  more  or  less  serious  and  painful 
character  lasting  for  years  and  even  decades,  while  others 
through  the  whole  of  a  long  life  have  hardly  a  moment 
in  which  they  are  not  aware  of  their  morbid  state, — the 
question  arises  what  meaning  there  can  be  in  a  life  which 
is  thus  dominated  by  disease.  How  can  we  accept  with 
equanimity  that  the  individual's  lot  should  be  so  extraor- 
dinarily variable,  that  one  should  suffer  without  cessation 
while  another  is  always  in  vigorous  health,  that  one  should 
attain  old  age  while  another  succumbs  prematurely? 

For  most  people  these  and  similar  considerations  are  de- 
cisive. They  ask  themselves  whether  a  life  which,  on 
account  of  illness,  has  offered  them  little  or  nothing  of 
the  good  things  which  others  have  enjoyed,  can  really  end 
with  death,  whether  there  is  not  to  be  a  continuation  in 
which  will  be  provided  a  compensation,  a  happiness  to 
make  up  for  that  which  is  here  denied  to  the  invalid. 
These  anxious  questionings  are  answered  by  the  religious 
systems,  which  hold  out  the  prospect  of  a  happy  eternal 
life  compensating  for  all  the  sufferings  endured  on  earth. 
Most  people  accept  this  prospect  as  certain.  Invalids  do 
not  indeed  appear  to  realise  that  when  they  enter  into 
eternal  happiness  the  balance  of  advantage  will  still  remain 
on  the  side  of  the  healthy,  for  the  sum  of  sickness  and 
happiness  is  always  less  than  the  sum  of  health  and  happi- 
ness. The  individual,  therefore,  can  never  be  fully  satis- 
fied by  the  explanation  that  illnesses  exist  in  order  to  direct 
people's  thoughts  to  the  life  beyond  the  grave  in  which 
compensation  will  be  provided  for  those  who  suffer  on 
earth.  Sickly  people  will  always  have  the  right  to  ask 
why  they  in  particular  should  have  been  selected  to  suffer 
on  earth,  and  to  this  the  only  possible  answer  is  that  God's 
ways  are  inscrutable. 

For  the  scientific  thinker  such  ideas  have  no  cogency. 


210  Heredity,  Disease  and  Human  Evolution 

From  the  outlook  of  science,  diseases,  like  all  other  natural 
processes,  are  necessary  phenomena  which  have  arisen  in 
the  course  of  the  evolution  of  the  organic  world  out  of 
the  conflict  between  individual  organisms  and  environmen- 
tal conditions,  out  of  the  struggle  for  existence.  In  the 
view  of  the  man  of  science,  diseases,  like  all  other  phe- 
nomena, must  be  judged  from  a  purely  objective  stand- 
point. He  can  find  nothing  in  the  existence  of  disease 
which  is  in  any  way  relevant  to  the  future.  He  regards 
diseases  as  occurrences  extremely  unfavourable  to  the  life 
and  the  evolution  of  the  human  race,  and  he  labours  to 
prevent  them  by  all  the  means  at  his  disposal.  He  knows 
that  the  dread  of  premature  death  has  a  paralysing  influ- 
ence upon  human  activities,  rendering  men  incompetent  to 
devote  themselves  wholeheartedly  to  the  purposes  of  life, 
and  incompetent  to  live  deliberately  and  unreservedly  for 
themselves  and  for  their  fellows.  But  the  fear  in  question 
depends  upon  the  existence  of  disease  and  the  occurrence 
of  premature  death.  Every  one,  therefore,  who  wishes  to 
allay  this  paralysing  fear,  as  must  every  one  who  has  at 
heart  the  progress  of  humanity,  will  urgently  desire  to 
do  all  in  his  power  to  put  an  end  to  disease.  To  the 
scientific  thinker,  illness  is  simply  a  disadvantageous  phe- 
nomenon whose  cessation  would  lead  to  an  untold  expan- 
sion of  our  racial  activities.  Perfect  bodily  and  mental 
health  is  therefore  the  goal  towards  which  he  strives. 

At  first  sight  it  might  appear  contradictory  that  we 
should  attempt  to  attain  the  ideal  of  universal  health, 
seeing  that  we  have  just  said  that  diseases  are  necessary 
phenomena  arising  out  of  the  struggle  with  environmental 
conditions.  It  is  useless,  we  shall  be  told,  to  struggle 
against  them,  since  they  are  inseparably  associated  with 
the  evolutionary  process.  But  this  applies  to  the  past  only. 
Diseases  can  be  regarded  as  inseparable  elements  of  the 
human  evolutionary  process  only  so  long  as  man  fails  to 
initiate  a  deliberate  endeavour  to  free  himself  from  them 
by  the  removal  of  the  unfavourable  environmental  condi- 


Disease  and  Religion  211 

tions  which  have  caused  them,  thus  conducting  the  struggle 
for  existence  into  paths  of  his  own  choosing.  When  he 
becomes  enabled  to  favour  his  own  evolutionary  process 
in  this  manner,  diseases  can  no  longer  be  regarded  as 
necessary  constituents  of  his  existence.  From  the  altitude 
of  insight  to  which  he  has  now  attained  man  is  enabled  to 
see  that  diseases  are  the  outcome  of  unfavourable  environ- 
mental influences,  and  that  to  an  increasing  extent  he  is 
becoming  competent  to  obviate  such  injurious  influences. 
Directly  he  understands  this,  he  recognises  the  inevitability 
of  the  fight  against  disease.  Insight  into  the  relationships 
between  himself  and  disease  is  a  product  of  the  evolu- 
tionary process  as  it  runs  its  course  in  himself  and  in 
humanity  at  large.  In  proportion  as,  in  virtue  of  this 
process,  which  is  in  all  respects  necessary  and  proceeds 
according  to  law,  man's  intellectual  faculties  are  per- 
fected, men  come  more  and  more  to  recognise  that  dis- 
eases are  not  essential  elements  of  their  nature,  but  are 
forced  on  them  from  without.  This  recognition,  in  turn, 
inevitably  leads  to  the  campaign  against  disease.  If  hith- 
erto disease  has  been  a  necessary  and  inseparable  accom- 
paniment of  the  general  course  of  evolution,  the  repression 
of  disease  has  now  become  no  less  necessary  and  inevitable. 
Thus  the  desire  to  do  away  with  disease  is  in  perfect 
harmony  with  the  process  of  human  evolution.  Humanity 
will  therefore  strive  by  all  possible  means  to  put  an  end 
to  pathological  states,  and  will  work  more  actively  to 
this  end  in  proportion  as  advance  is  made  in  the  direction 
of  its  attainment.  For  as  that  advance  is  effected  men 
will  feel  ever  more  keenly  the  tragedy  of  their  present 
condition,  the  abolition  of  which  is  the  sublimest  task  of 
our  race.  If  the  ideal  of  universal  health  were  ever  at- 
tained, it  would  no  longer  be  disease  and  premature  death, 
but  simply  the  normal  life  of  mankind  that  would  deter- 
mine men's  conceptions  of  their  relationship  to  the  uni- 
verse. Then  man  would  be  freed  from  all  the  disadvan- 
tages— and  they  are  many — which  are  entailed  upon  our 


212  Heredity,  Disease  and  Human  Evolution 

race  by  the  now  dominant  religious  systems  in  so  far  as 
the  doctrines  of  these  are  the  outcome  of  the  existence  of 
disease.  If  the  religions  did  no  more  than  to  gratify  with 
hopes  for  the  future,  all  those  individuals  who  feel  the 
need  for  such  hopes,  if  they  merely  endeavoured  to  help 
people  with  the  idea  that  in  some  alluring  future  beyond 
the  grave  there  will  be  found  compensation  for  illness  and 
premature  death,  no  one  need  offer  any  objection. 

But  the  religious  systems  are  not  satisfied  with  the  in- 
culcation of  such  wide  general  views.  They  do  not  ask 
merely  that  the  thoughts  of  sick  persons  should  be  turned 
in  the  religious  direction,  but  they  insist  upon  the  ac- 
ceptance of  definite  creeds.  They  tell  us  that  a  happy  life 
is  possible  only  through  the  observance  of  certain  strict 
religious  commandments,  and  that  we  must  believe  all 
their  doctrines  with  as  little  reflection  as  possible  on  our 
own  part.  The  invalids  who  fear  death,  and  those  who 
see  the  sufferings  of  their  fellow  men  and  upon  whom  simi- 
lar fears  are  thereby  imposed,  yield  to  their  demands.  Thus 
men  are  brought  to  believe  in  the  rigid  dogmas  of  ortho- 
doxy, whose  strongest  props  are  diseases.  Without  this 
support,  the  dogmas  would  crumble  away. 

It  may  here  be  suggested  that  we  have  no  right,  in 
this  connexion,  to  think  of  illness  alone.  All  the  other 
kinds  of  human  suffering  furnish  an  impulse  to  religious 
thought.  More  particularly  is  this  true  of  the  tragical 
social  conditions  that  arise  from  poverty.  But  how  does 
poverty  come  into  existence?  It  arises  in  great  part  be- 
cause disease  has  prevailed  in  the  family,  because  one  or 
both  parents  have  fallen  ill,  and  are  therefore  unable  to 
earn  their  bread,  or  because  one  or  several  children  are 
ill.  To  a  still  greater  extent  poverty  ensues  because  per- 
sons have  a  defective  intellectual  equipment,  are  not  com- 
pletely normal,  and  are  therefore  incompetent  to  cope  with 
unfavourable  conditions.  Thus  it  will  be  seen  that  dis- 
ease and  abnormal  mental  predisposition  play  a  large  part 
in  the  causation  of  the  sufferings  consequent  upon  poverty. 


Disease  and  Religion  213 

We  must,  indeed,  admit  that  there  are  some  persons  who 
remain  poor,  or  become  poor,  owing  to  unfavourable  ex- 
ternal conditions  among  which  illness  or  mental  abnor- 
mality plays  no  part.  But  in  such  cases  is  it  really  the 
insufficiency  of  the  means  of  life  that  per  se  turns  the 
mind  towards  religion?  Is  not  this  direction  of  the 
thoughts  due  rather  to  the  fact  that  body  and  mind  have 
been  injured  by  insufficient  and  erroneous  nutrition,  and 
have  thus  become  diseased?  Unquestionably  this  is  so. 
Starvation  and  underfeeding,  even  if  they  do  not  induce 
actual  disease,  similarly  impair  the  human  faculties,  and 
the  unceasing  cares  of  existence  and  the  need  of  a  man's 
dependents  are  a  continued  source  of  irritation,  leading  to 
mental  abnormality,  and  gravely  impairing  the  powers  of 
resistance.  Thus  where  there  is  poverty  or  destitution 
men's  thoughts  and  feelings  are  determined  by  bodily 
and  mental  abnormality. 

We  must  therefore  reiterate  that  it  is  a  state  of  disease 
which  leads  human  beings  to  take  refuge  under  the  shelter 
of  dogmatic  systems. 

These  systems  are  thus  dependent  upon  disease.  There 
can  be  no  doubt  that  most  of  their  adherents  accept  them 
mainly  because  they  hope  to  find  in  them  relief  from  the 
anxieties  aroused  by  disease  and  death,  and  because  on 
the  average  they  do  actually  find  such  relief.  With  the 
cessation  of  disease  there  would  be  removed  a  powerful 
motive  which  now  leads  men  to  turn  towards  dogmatic 
religion.  It  is  unquestionable  that  if  men  were  all  healthy 
they  would  be  much  less  concerned  than  they  are  at  pres- 
ent, and  perhaps  not  concerned  at  all,  about  the  question 
of  life  after  death ;  certainly  they  would  not  trouble  them- 
selves about  dogmatic  teachings,  which  have  been  born 
solely  out  of  the  fear  of  premature  death.  Death  in  old 
age,  as  the  painless  end  of  a  healthy  life,  would  no  longer 
make  a  powerful  impression  on  the  mind.  Such  a  death 
would  not  be  feared,  whereas  death  as  we  know  it  to-day, 
usually  premature,  induced  by  disease,  and  preceded  by 


214  Heredity,  Disease  and  Human  Evolution 

severe  suffering,  is  the  cause  of  much  disquiet.  When 
our  race  has  attained  health,  the  thought  of  what  is  beyond 
death  will  not  trouble  the  old  man  who  looks  back  from 
the  end  of  a  happily  completed  life ;  such  a  one  will  simply 
desire  the  peace  of  death.  This  is  what  we  commonly 
see  even  to-day  in  old  age ;  and  we  should  see  it  still  more 
frequently  were  it  not  that  from  youth  upwards  people's 
minds  are  perpetually  redirected  towards  orthodox  views 
by  the  force  of  current  teaching  and  by  the  premature 
deaths  of  their  associates.  When  all  men  are  healthy  and 
when  death  occurs  solely  in  old  age,  the  interest  in  dog- 
matic religious  teachings  will  decline  and  disappear.  Even 
as  things  are,  the  relatives  of  one  who  dies  in  advanced 
age  hardly  ever  regard  this  event  as  an  occasion  for  re- 
ligious reflections.  They  view  an  old  man 's  death  primarily 
as  a  release  from  the  troubles  of  old  age.  They  consider 
such  a  death  to  be  a  natural  process,  and  see  in  it  no 
ground  for  complaint. 

If  all  human  beings  were  perfectly  healthy,  or  in  other 
words  if  there  were  no  illness,  the  perfect  normality  of 
our  condition  would  allay  the  fear  of  death,  and  therewith 
would  remove  the  principal  cause  of  anxiety  about  a  life 
beyond  the  grave.  Even  the  consideration  of  possible 
eternal  punishment  for  evil  deeds  and  thoughts  would 
lose  its  terrors,  for  the  healthy  human  being,  harmoniously 
developed,  could  no  longer  perform  acts  which  could  be 
described  as  evil  in  the  sense  of  existing  religious  doc- 
trines. Acts  of  this  character  (see  p.  40)  are  the  out- 
come solely  of  a  morbid  condition,  or  at  any  rate  of  one 
that  is  not  perfectly  normal.  The  man  who  is  thoroughly 
healthy  in  every  respect  simply  cannot  act  badly  or  wick- 
edly; his  actions  are  necessarily  good,  necessarily,  that  is 
to  say,  properly  adapted  to  the  evolution  of  the  human 
race,  in  harmony  with  the  cosmos.  Man  would  therefore 
have  no  occasion  to  dread  such  punishments  beyond  the 
grave  as  dogmatic  religion  is  accustomed  to  depict  for  us 
to-day;  the  idea  of  expecting  rewards  and  punishments 


Disease  and  Religion  215 

after  death  is  one  which  would  never  enter  his  mind. 
For  this  reason  he  would  be  altogether  inaccessible  to  ortho- 
dox religious  views. 

If  the  disappearance  of  disease  will  thus  diminish  or 
remove  anxiety  about  the  life  beyond,  the  adherents  of  the 
dogmatic  systems  cannot  logically  be  expected  to  desire 
that  the  existing  morbid  condition  of  our  race  should  be 
replaced  by  a  healthy  one,  for  should  this  happen  the  num- 
ber of  the  faithful  would  continually  diminish.  In  this 
matter,  however,  men's  desires  are  stronger  than  the  inter- 
ests of  dogma.  Every  one  strives  to  be  healthy,  and  even 
the  strictest  advocates  of  the  orthodox  views  do  not  differ 
in  this  respect  from  their  fellow  men.  But  if  the  abolition 
of  disease  should  ever  be  successfully  accomplished,  in  the 
healthy  human  being  the  need  for  rigid  dogmatic  religious 
ideas  would  become  less  and  less  conspicuous,  and  the  re- 
ligious systems  would  spontaneously  tend  to  grow  less  dog- 
matic. 

For  the  present,  indeed,  dogma  still  dominates,  and  the 
adherents  of  dogma  will  do  their  best  to  maintain  its  do- 
minion. It  cannot  be  doubted  that  they  will  succeed.  The 
great  majority  of  men  will  continue  to  cleave  to  dogma; 
some  because  their  intellectual  powers  are  inadequate  to 
enable  them  to  regard  disease  objectively,  others  because 
they  are  not  inclined  to  do  this,  being  influenced  by  the 
contemplation  of  their  own  and  others'  suffering  and  by 
the  sight  of  premature  death;  they  are  thus  led  to  accept 
dogma  with  its  peculiar  attitude  towards  death  and  its 
promise  of  a  life  beyond  the  grave.  For  these  reasons  the 
empire  of  dogma  will  be  long-enduring,  and  the  power  of 
the  orthodox  systems  will  not  soon  be  broken.  If  all  that 
dogma  affected  were  simply  to  provide  consolation  for 
those  who  to-day  accept  dogma,  for  those  who  without 
dogma  could  not  find  satisfaction  or  would  be  positively 
unhappy,  to  make  them  unrepiningly  accept  the  existence 
of  illness  and  consequent  poverty,  this  influence  is  one  we 
could  not  fail  to  welcome.     The  freethinker  would  have 


216  Heredity,  Disease  and  Human  Evolution 

no  interest  in  depriving  of  this  solace  those  who  can  find 
it  only  in  dogmatic  teachings.  Enlightenment  at  any  cost 
can  be  the  aim  of  those  alone  who  are  dogmatists  in  their 
turn,  and  are  therefore  just  as  one-sided  as  the  advocates 
of  the  rigid  religious  systems. 

"While,  however,  within  its  own  domain,  dogma  may  be 
of  advantage  to  many  persons,  we  cannot  admit  the  claim 
made  by  the  adherents  of  dogma  that  all  those  ought  to 
accept  it  who  have  in  actual  fact  cast  off  its  shackles, 
and  who  have  come  to  regard  diseases  simply  as  phe- 
nomena existing  in  accordance  with  natural  law.  Those 
who  take  this  latter  view  have  just  as  much  right  to  their 
own  opinion  as  the  dogmatists.  They  must  demand  that 
all  men,  whatever  religious  views  they  may  hold,  should 
possess  exactly  the  same  rights  in  private  and  public  life. 
If  this  were  granted,  how  much  would  be  gained  even 
to-day,  when  diseases  and  dogmas  are  still  in  power.  But 
we  are  as  yet  far  from  this  consummation,  for  the  ortho- 
dox systems  will  not  admit  any  such  claim. 

Dogma  is  essentially  intolerant.  It  lies  in  its  very 
nature,  not  merely  to  reject  all  other  views  than  its  own, 
but  to  fight  against  them  energetically.  Thus  arise  con- 
flicts characterised  by  extreme  violence. 

"We  do  not  mean  to  imply  that  all  adherents  of  dogma 
must  as  individuals  necessarily  be  intolerant.  For  dogma 
is  foreign  to  man's  nature,  and  not  in  every  one  is  the 
love  of  dogmatising  so  keen  as  to  lead  to  the  suppression 
of  our  instinctive  desire  to  live  at  peace  with  our  fellow 
men.  Many,  however,  are  intolerant.  Some  because  they 
want  to  convert  every  one  else  to  the  opinion  that  seems 
to  them  the  only  right  one,  forgetting  that  belief  is  sub- 
jective in  character  and  cannot  be  constrained.  Others, 
and  these  unfortunately  are  very  numerous,  are  intolerant 
from  lack  of  sympathy,  hatred,  love  of  dominion,  and 
other  unworthy  motives — and  above  all  because  they  are 
not  perfectly  normal  or  because  they  are  definitely  dis- 
eased. 


Disease  and  Eeligion  217 

Further  discussion  of  intolerance  and  its  disastrous  con- 
sequences is  outside  the  scope  of  this  work.  The  signifi- 
cance of  dogma  is  known  to  all.  "We  may  simply  refer  to 
the  history  of  the  inquisition,  to  the  persecution  of  heretics 
and  Jews,  to  the  fierce  struggles  between  the  adherents  of 
the  different  creeds,  to  the  disunion  sown  by  divergent 
dogmas  in  the  nation  and  in  the  family.  Such  conse- 
quences are  matters  of  everyday  experience.  They  serve 
more  than  all  else  to  poison  the  springs  of  private  and 
of  public  life,  and  to  rend  humanity  asunder. 

The  ultimate  cause  of  such  deplorable  intolerance  is  the 
existence  of  disease  and  of  premature  death.  Without 
these  there  would  be  no  dogma,  and  without  dogma  there 
would  be  no  intolerance.  Thus  from  this  point  of  view 
also  a  campaign  for  the  abolition  of  disease  is  seen  to 
be  absolutely  essential.  Religious  peace  on  the  foundation 
of  undogmatic  views  will  not  be  attained  until  disease 
has  been  greatly  restricted  in  extent  or  has  altogether  dis- 
appeared. 


CHAPTER  IX 

THE  ABOLITION  OP  DISEASE.     RACIAL  HYGIENE 

At  the  close  of  the  sixth  chapter  we  said  it  was  ques- 
tionable whether  there  was  any  serious  reason  to  dread 
the  much-discussed  danger  that  the  human  race  is  under- 
going degeneration,  hut  we  added  that  even  if  this  danger 
be  imaginary  we  must  none  the  less  do  everything  in  our 
power  to  effect  the  abolition  of  disease.  The  whole  course 
of  this  discussion  has  shown  us  that  the  injuries  inflicted 
by  disease  are  enormous  and  that  they  cannot  possibly 
be  overestimated.  Even  if  diseases  should  not  become 
more  frequent  than  they  are  to-day,  their  continued  preva- 
lence would  greatly  interfere  with  the  future  evolution 
of  our  race.  For  this  reason  the  campaign  against  dis- 
ease is  a  duty.    What  steps  can  we  take  to  this  end  ? 

It  is  obvious  that  we  must  devote  our  attention  above 
all  to  the  abolition  of  hereditary  morbid  states.  These  are 
by  far  the  most  important  in  relation  to  human  evolution, 
because  they  affect  men  throughout  the  whole  of  life, 
because  their  association  with  life  is  so  intimate  that  they 
seem  as  it  were  to  become  a  part  of  our  being,  because 
they  touch  us  so  intimately,  and  because  they  may  be  trans- 
mitted by  us  to  our  offspring.  If  the  alleged  racial  degen- 
eration were  really  in  progress,  this  must  depend  upon 
hereditary  diseases,  for  other  diseases  would  come  into  the 
question  only  so  far  as  they  were  qualified  to  give  rise  to 
new  transmissible  pathological  characteristics.  As  far, 
however,  as  the  welfare  of  each  generation  is  concerned,  the 
individual  diseases  also  play  a  great  part. 

When  we  speak  of  doing  away  with  illnesses  we  com- 

218 


The  Abolition  of  Disease  219 

monly  think  first  of  all  of  their  cure.  But  cure  comes 
in  question  onl,y  as  regards  non-hereditary  infections,  and 
unfortunately  only  as  regards  a  minority  of  these.  It  is 
true  that  there  are  many  illnesses  in  which  so  complete  a 
cure  may  result  that  often  not  the  least  trace  remains; 
this  applies  to  the  acute  infectious  diseases,  acute  pneu- 
monia, typhoid,  the  infectious  diseases  of  childhood,  wound- 
infections,  injuries,  etc.  Yet  we  all  know  that  even  as 
far  as  these  diseases  are  concerned  not  a  few  attacks  end 
in  death,  and  that  even  if  recovery  occurs  it  is  by  no 
means  rare  for  some  morbid  condition  to  remain  as  a 
sequel.  There  are  many  other  diseases  in  which  recovery 
does  not  take  place,  or  is  quite  exceptional,  for  example, 
valvular  disease  of  the  heart,  contracting  kidney,  calcifica- 
tion of  the  arteries,  the  malignant  tumours,  severe  tuber- 
culosis, etc.  By  these  diseases,  moreover,  because  their 
course  is  usually  a  long  one,  and  because  the  functional 
activity  of  those  affected  is  seriously  impaired  or  com- 
pletely arrested,  humanity  is  far  more  seriously  injured 
than  by  acute  curable  illnesses,  for  the  latter,  though  ab- 
solutely more  frequent  than  the  others,  are  relatively 
transient  in  duration. 

As  regards  all  these  maladies,  our  principal  task  is 
prevention.  Since  in  the  case  of  most  of  them  we  have 
to  do  with  infectious  diseases  and  their  consequences,  or 
with  intoxications,  it  must  be  our  aim  to  ward  off  the  at- 
tacks of  micro-organisms  and  to  avoid  the  ingestion  of 
poisons.  In  this  matter  of  prophylaxis,  as  we  term  it,  we 
have  made  much  progress,  at  any  rate  in  the  case  of  some 
of  the  infectious  diseases.  Typhoid  and  cholera  have 
become  much  rarer,  having  been  almost  suppressed  in 
northern  Europe,  and  the  frequency  of  tuberculosis  has 
been  somewhat  reduced. 

Hereditary  morbid  states  must  however  also  be  num- 
bered among  the  incurable  diseases.  Since  they  are  affec- 
tions of  the  germ,  and  are  therefore  rooted  in  the  indi- 
vidual's constitution,  they  are  beyond  the  physician's  in- 


220  Heredity,  Disease  and  Human  Evolution 

fluence.  Congenital  malformation,  colour-blindness,  haemo- 
philia, hereditary  diabetes,  hereditary  gout,  inherited  men- 
tal disorder,  and  the  various  other  pathological  conditions 
handed  down  from  progenitors  to  offspring,  are  beyond 
cure.  If  such  diseases  were  really  increasing  in  preva- 
lence and  thus  leading  to  the  degeneration  of  our  race, 
therapeutics  would  be  impotent  in  the  matter. 

Since  this  is  so  we  must  adopt  other  methods.  First  of 
all  we  have  to  consider  the  possibility  of  preventing  as 
far  as  may  be  the  new  appearance  of  hereditary  diseases. 
To  this  end  we  must  employ  in  part  the  same  means  that 
we  employ  against  accidental  diseases,  means  which  have 
already  been  described,  for  the  acute  infectious  processes 
are  competent  to  injure  the  germinal  cells.  Their  pre- 
vention would  obviate  this  danger,  and  thus  a  number 
of  hereditary  abnormal  conditions  would  cease  to  be  pro- 
duced. Think,  for  example,  of  syphilis,  whose  effect  upon 
the  germinal  cells  experience  shows  to  be  extremely  in- 
jurious. Thus  a  perfected  system  of  hygiene  would  serve 
to  prevent,  not  merely  the  acute  diseases,  but  also  the 
occurrence  of  injuries  to  the  germ.  We  have  shown  above 
(p.  178)  that  there  is  no  danger  that  this  would  have  the 
effect  of  removing  a  valuable  selective  influence.  Nor,  in 
this  connexion,  must  we  confine  our  attention  to  the  infec- 
tious diseases.  It  is  necessary  to  refer  once  more  to  alcohol, 
the  influence  of  which  in  poisoning  the  germ,  an  influence 
whose  importance  is  variously  estimated,  was  discussed  in 
an  earlier  chapter  (p.  161).  In  view  of  these  hereditary 
possibilities,  we  must  do  our  utmost  to  put  a  stop  to  the 
misuse  of  alcohol.  In  this  respect  the  state  and  the  com- 
munity-at-large  have  important  duties  to  fulfil. 

In  these  fields  of  prophylaxis  much  can  unquestionably 
be  done  to  diminish  the  prevalence  of  hereditary  morbid 
tendencies,  although  the  attainment  of  our  aims  in  this 
respect  will  be  slowly  effected.  In  this  way,  however,  a 
part  only  of  our  task  will  be  performed.  A  no  less  im- 
portant part  remains,  namely,  to  prevent  procreation  by 


The  Abolition  of  Disease  221 

persons  who  are  affected  with  severe  inheritable  diseases. 
I  emphasise  the  term  severe,  for  it  is  upon  the  severe 
eases  that  we  must  first  concentrate  attention.  It  would  be 
a  mistake  to  divide  our  forces.  As  regards  colour-blindness, 
shortsightedness,  the  minor  malformations,  and  the  like,  we 
shall  have  no  useful  opportunity  of  limiting  procreative 
activity.  We  are  primarily  concerned  with  graver  con- 
ditions, those  that  make  the  individual  affected  with  them 
worthless,  useless,  and  a  positive  danger  to  his  fellows,  such 
as  the  different  forms  of  mental  disease  and  of  criminality. 
We  should  aim  at  excluding  from  reproduction,  not  only 
those  who  are  already  themselves  ill  in  the  sense  just  de- 
fined, but  those  also  who,  though  not  themselves  severely 
affected,  are  in  a  condition  which  involves  the  danger  of 
such  injury  of  the  germinal  cells  and  therewith  to  the 
offspring  as  is  likely  to  result  in  these  latter  being  affected 
with  mental  disorder.  We  think  here  especially  of  drunk- 
ards. Even  if  we  do  not  regard  as  proved  all  the  evils 
that  have  been  laid  to  the  charge  of  alcohol,  still  no  one 
can  doubt  that  the  persistent  soaking  of  the  body  with 
this  poison  must  involve  injury  to  the  germinal  cells. 

What  are  we  able  to  do  in  the  way  of  preventing  pro- 
creation ? 

Much  is  effected  by  certain  measures  which  are  not  un- 
dertaken in  the  express  aim  of  preventing  reproductive 
activity,  as,  for  example,  by  the  permanent  seclusion  ol' 
lunatics  in  asylums  and  the  confinement  of  criminals  in 
prisons  and  penitentiaries.  Such  means,  however,  are  in- 
adequate. Many  mental  disorders  develop  slowly,  and  the 
persons  affected  with  these  may  have  children  before  they 
are  placed  under  restraint.  Since,  however,  the  morbid 
condition  already  affects  their  germinal  cells,  they  trans- 
mit the  taint  at  a  period  when  they  themselves  still  ap- 
pear healthy.  Other  persons  suffering  from  mental  dis- 
order are  discharged  from  institutions  although  they  are 
not  cured  in  the  proper  sense  of  the  term,  whilst  others 
live  always  with  their  families.     Criminals  for  the  most 


222  Heredity,  Disease  and  Human  Evolution 

part  are  confined  for  a  time  merely,  and  can  reproduce 
their  kind  as  soon  as  they  are  set  at  liberty.  If,  there- 
fore, we  wished  to  attain  our  end  by  means  of  the  segre- 
gation of  tainted  individuals,  the  only  course  open  to  us 
would  be  the  permanent  seclusion  of  all  those  affected  with 
severe  mental  disorder,  and  of  all  the  criminals  who  have 
taken  to  criminal  courses  because  they  have  developed  from 
diseased  germinal  cells,  so  that  we  must  suppose  the  germi- 
nal cells  in  their  bodies  to  be  also  tainted. 

Another  proposal  that  has  been  made  is  that  such  mental 
invalids  should  not  be  locked  up,  but  that,  in  so  far  as 
they  are  suited  (as  are  criminals)  for  the  application  of 
this  method,  they  should  be  deported  to  colonies  where 
(since  the  sexes  will  be  segregated)  they  will  have  no  op- 
portunity of  reproducing  their  kind. 

Especially  effective  is  the  practice  of  castration  in  males 
and  of  oophorectomy  in  females,  that  is  to  say  the  opera- 
tive removal  of  the  reproductive  glands;  or  simple  sterili- 
sation by  a  much  easier  and  less  severe  operation,  the  divi- 
sion of  the  canals  by  which  the  germinal  cells  are  dis- 
charged, the  Fallopian  tubes  in  women  and  the  vasa  defer- 
entia  in  men.  In  some  of  the  states  of  the  American 
union  such  operations  have  been  practised,  in  certain 
cases  on  criminals  exclusively,  but  in  others  also  on  im- 
beciles and  the  weak-minded.  In  the  State  of  Indiana,  ac- 
cording to  a  report  by  Hans  W.  Maier,  at  the  end  of  July, 
1911,  873  persons  had  been  sterilised  by  operation.  In 
Switzerland,  also,  as  we  learn  from  Oberholzer,  a  begin- 
ning has  been  made  in  the  adoption  of  such  measures. 

We  must  further  consider  the  question  of  prohibiting 
marriage  in  the  case  of  all  persons  who  suffer  from  severe 
hereditary  disorders.  Many  of  the  states  of  the  American 
union  have  set  a  good  example  in  this  respect.  Maier  in- 
forms us  that  marriage  laws  of  this  character  have  been 
passed  in  Connecticut,  Michigan,  Ohio,  Kansas,  New  Jer- 
sey and  Minnesota.  These  laws  deal  especially  with  luna- 
tics, epileptics,  the 'feeble-minded,  and  drunkards,  to  some 


The  Abolition  of  Disease  223 

extent  even  where  the  affection  no  longer  remains  active, 
but  where  there  is  danger  of  relapse  or  of  the  existence  of 
simultaneous  disease  of  the  germinal  cells.  In  Michigan  it 
is  also  a  punishable  offence  to  assist  in  the  marriage  of 
individuals  suffering  from  inheritable  disease. 

All  such  endeavours  for  the  diminution  of  hereditary 
disease  find  numerous  advocates  in  Germany,  England, 
and  throughout  northern  Europe.  In  Germany  those  who 
favour  these  aims  have  formed  a  Society  for  the  Promo- 
tion of  Racial  Hygiene  {Gesellschaft  fiir  Rassenhygiene) . 
Its  activities  centre  in  Munich,  and  its  president  is  Dr. 
Ploetz.  The  scientific  aspect  of  the  matter  is  discussed  in 
the  Archiv  fiir  Rassen-  und  Gesellschaft sMologie,  now  in  its 
tenth  year  of  issue.  In  England  the  first  concrete  expres- 
sion of  the  tendency  to  promote  racial  hygiene  was  the 
work  of  Francis  Galton,  to  whom  we  owe  the  term  "eu- 
genics." There  exists  in  London  a  Eugenics  Laboratory, 
and  by  this  institution  have  been  issued  the  researches  into 
inheritance,  and  the  detailed  pedigrees,  to  which  allusion 
has  several  times  been  made,  contained  in  A  Treasury  of 
Human  Inheritance.  An  international  association  has  been 
formed  to  co-ordinate  the  activities  of  the  advocates  of 
racial  hygiene  in  the  various  countries  we  have  named. 

We  owe  to  Schallmeyer  a  remarkable  work  dealing  with 
all  these  questions  which  was  published  in  the  year  1910 
under  the  title  Vererhung  und  Auslese  (Heredity  and  Se- 
lection). 

All  such  efforts  to  limit  the  prevalence  of  hereditarily 
transmissible  diseases  deserve  cordial  support.  No  one  who 
is  interested  in  the  further  advance  of  human  evolution 
should  neglect  this  field  of  activity. 

Unfortunately,  however,  the  goal  is  less  easy  to  attain 
than  might  at  first  sight  appear.  For,  first  of  all,  the  con- 
siderations upon  which  action  is  based  have  not  yet  per- 
meated those  circles  which  are  chiefly  responsible  for  leg- 
islation. In  European  countries  there  is  at  present  hardly 
any  prospect  of  measures  to  deal  with  the  danger  of  the 


224  Heredity,  Disease  and  Human  Evolution 

hereditary  transmission  of  severe  mental  disorder  and 
criminal  tendencies.  Nor  is  there  any  near  prospect  of 
the  institution  of  marriage  prohibitions  similar  to  those 
that  exist  in  some  of  the  United  States.  A  considerable 
time  must  elapse  before  the  Society  for  Racial  Hygiene 
will  have  been  able  to  disseminate  its  ideas  through  wide 
circles.  At  present  among  the  general  public  there  un- 
fortunately exists  very  little  serious  inclination  to  accept 
the  imposition  of  any  kind  of  legislative  restriction  upon 
the  procreation  of  children,  although — and  here  the  same 
circle  of  ideas  is  really  involved — errors  of  omission  in  the 
way  of  the  deliberate  limitation  of  the  family  are  extraor- 
dinarily widespread.  In  this  matter  also  we  have  to  rec- 
ognise an  indication  of  the  comparative  worthlessness  of 
innumerable  human  beings.  We  cannot  regard  as  normal 
individuals  those  who  restrict  the  procreation  of  children 
on  the  ground  of  convenience.  The  woman's  movement 
also  is  partly  to  blame  for  this.  One-sided,  extreme,  and 
therefore  abnormal  advocates  of  woman's  emancipation 
commonly  renounce  marriage,  and  therewith  refuse  to  un- 
dertake woman's  chief  duty,  that  of  motherhood. 

It  is  true  that  the  limitation  of  the  family  has  been 
advocated  for  other  reasons,  which  in  many  cases,  how- 
ever, are  certainly  no  more  than  a  mask  for  the  personal 
convenience  of  the  parents.  The  neomalthusian  doctrine 
refers  to  the  danger  of  over-population,  and  to  the  fact 
that  when  there  are  too  many  children  in  a  family  extreme 
poverty  is  apt  to  ensue.  We  cannot  consider  this  matter 
here,  and  will  merely  point  out  that  the  superficial  and 
uncritical  manner  in  which  the  demand  for  the  limitation 
of  the  family  is  voiced  on  all  hands  involves  a  grave  dan- 
ger to  human  evolution.  The  danger  consists  in  this,  that 
too  small  a  number  of  vigorous  offspring  will  be  procre- 
ated. Interference  with  procreation  on  such  lines  is  justi- 
fied in  so  far  as  its  aim  is  to  prevent  the  exercise  of  repro- 
ductive activity  by  badly  qualified  parents,  but  it  is  alto- 
gether without  justification  in  so  far  as  it  influences  those 


The  Abolition  of  Disease  225 

individuals  who  are  in  all  respects  apt  for  procreation, 
and  who,  precisely  in  consequence  of  their  healthy  constitu- 
tion, are  also  fully  competent  to  rear  a  large  family  with 
success.  One  of  the  important  tasks  of  racial  hygiene  is  to 
see  to  it  that  such  parents  shall  not  procreate  too  small  a 
number  of  children,  to  ensure,  that  is  to  say,  that  in  such 
instances  the  neomalthusian  doctrine  shall  not  find  practi- 
cal application.  The  limitation  of  the  family  must  not  be 
pursued  in  this  uncritical  manner.  The  system  must  be 
applied  only  in  the  case  of  individuals  affected  with  hered- 
itary disease.  Here,  however,  the  application  must  be 
radical.  Hereditary  invalids  should  have  no  children  at 
all.  But  such  an  end  is  attainable  only  through  mar- 
riage prohibitions,  although  not  completely  even  by  these. 
"We  have  already  pointed  out  that  the  time  is  not  yet 
ripe  for  legislation.  Objection  to  such  measures  is  often 
raised  on  the  ground  that  our  scientific  knowledge  of 
heredity  is  not  sufficiently  full  and  accurate  to  furnish  us 
with  firm  grounds  for  action.  If  we  are  to  prevent  pro- 
creation we  must  have  positive  assurance  that  the  off- 
spring, if  conceived,  would  really  be  diseased.  In  default 
of  such  certainty,  we  are  not  justified  in  instituting  pro- 
hibitions. This  is  obvious.  In  actual  fact,  our  knowledge 
of  the  laws  of  heredity,  especially  as  regards  disease,  is 
inadequate,  and  we  have  to  admit,  as  a  fact  of  general  ex- 
perience, that  the  children  of  diseased  persons  are  by  no 
means  all  necessarily  diseased.  It  may  be  pointed  out  that 
in  accordance  with  the  law  of  the  segregation  of  characters 
we  often  find  that  not  more  than  one  half  of  the  children  be- 
come ill.  Hence,  we  are  told,  we  have  no  right  to  inter- 
fere with  procreation.  But  is  it  contended,  we  must  ask, 
that  the  healthy  children  and  the  diseased  weigh  down  the 
scales  equally?  Is  it  not  rather  true  that  the  disadvan- 
tages entailed  by  the  existence  of  the  diseased  are  far 
greater  than  the  advantages  entailed  by  the  existence  of 
the  healthy  offspring?  Do  not  the  sickly  children  consti- 
tute a  permanent  reproach  to  the  parents,  so  that  the  fact 


226  Heredity,  Disease  and  Human  Evolution 

that  some  of  their  offspring  are  healthy  cannot  suffice  to 
absolve  the  parents  from  blame  ? 

Moreover,  Mendelian  segregation  is  valid  as  regards  a 
part  only  of  hereditary  conditions.  It  occurs  in  the  less 
severe  types  of  disease,  and  in  those  that  are  of  less 
importance  from  the  point  of  view  of  degeneration,  such 
as  the  minor  anomalies  and  malformations.  It  is  seen  also 
in  hemophilia,  diabetes,  and  (according  to  the  latest  evi- 
dence) in  certain  mental  disorders  as  well.  But,  as  far  as 
our  present  knowledge  goes,  segregation  does  not  occur 
in  the  case  of  the  most  severe  forms  of  mental  disorder  and 
in  that  of  hereditary  tendencies  to  crime.  In  such  in- 
stances it  often  happens  that  all  the  offspring  are  abnormal, 
although  in  varying  degrees,  so  that  it  would  seem  that 
the  separation  of  the  diseased  from  the  healthy  character 
has  here  been  difficult  to  effect.  This  may  possibly  depend 
upon  the  fact  that  whereas  in  slighter  cases  only  a  single 
organ  undergoes  morbid  change,  in  these  severe  forms  of 
germinal  intoxication  the  whole  body  is  diseased.  If  this 
be  so,  complete  segregation  will  far  less  easily  occur.  If 
we  conceive  that  the  germinal  intoxication  has  affected  a 
whole  series  of  separate  characters,  and  if  we  imagine 
that  when  segregation  occurs  each  of  these  characters  be- 
haves independently,  the  result  is  likely  to  be  that  instead 
of  all  the  normal  rudiments  entering  one  germinal  cell  and 
all  the  abnormal  rudiments  another,  one  germinal  cell  will 
receive  some  morbid  characters  while  another  germinal  cell 
will  receive  others.  This  would  explain  why  it  is  that 
all  the  offspring  are  diseased,  but  that  they  are  affected 
in  different  ways. 

The  absolute  prohibition  of  procreation  is  obviously  nec- 
essary in  all  cases  in  which  complete  segregation  does 
not  occur.  For  as  far  as  these  instances  are  concerned 
there  is  lacking  even  the  questionable  excuse  that  some 
of  the  offspring  may  possibly  remain  healthy. 

But  supposing  that  among  the  offspring  of  diseased  pro- 
genitors of  any  particular  generation  not  all  are  diseased, 


The  Abolition  of  Disease  227 

what  should  the  healthy  individuals  do?  In  view  of  the 
experience  noted  above  (p.  132)  that  in  the  ease  of  direct 
inheritance  (inheritance  without  skipping  a  generation)  the 
offspring  of  those  children  not  themselves  diseased  often 
remain  permanently  healthy,  may  not  such  persons  marry 
without  anxiety?  In  those  diseases  in  which  complete 
segregation  is  the  rule  there  is  certainly  no  harm  in  this. 
As  we  have  just  seen,  however,  it  is  not  these  diseases  with 
which  we  are  chiefly  concerned  in  connexion  with  degen- 
eration. In  the  more  serious  forms  of  germinal  intoxica- 
tion the  danger  is  ever  present  that  the  non-aft*ected  mem- 
bers of  the  family  may  harbour  the  disease  in  a  latent 
state,  for  the  reason  that  the  segregation  of  characters  has 
not  been  complete,  so  that  some  abnormal  character  or 
other  remains  attached  to  the  germ  without  manifesting  its 
presence  either  in  the  individuals  themselves  or  in  their 
immediate  offspring.  In  subsequent  generations,  however, 
this  character  once  more  becomes  manifest.  We  shall  un- 
derstand this  without  difficulty  if  we  recall  that  in  the 
case  of  hemophilia  the  female  members  of  the  affected 
family  carry  the  anomaly  in  their  germinal  cells  and  trans- 
mit it  to  their  male  children  without  personally  suffering 
from  the  disease.  Hence  when  we  have  to  do  with  ger- 
minal intoxications  each  individual  case  must  be  examined 
on  its  merits. 

The  opponents  of  marriage  prohibitions  will  tell  us  that 
the  marriage  of  members  of  diseased  families  with  the 
members  of  healthy  families  is  permissible,  because  experi- 
ence has  shown  that  the  healthy  condition  may  be  compe- 
tent to  extinguish  the  diseased.  It  is  true  that  this  occurs, 
but  by  no  means  as  a  rule.  It  suffices  to  point  out  that 
the  female  members  of  families  affected  with  hemophilia 
when  married  to  healthy  men  procreate  children  who  suffer 
from  this  disease.  In  such  marriages,  therefore,  it  is  im- 
possible to  count  upon  the  extinction  of  the  morbid  state. 

Still  more  necessaiy  is  it  to  forbid  marriage  when  neither 
party  to  the  proposed  union  is  normal,  or  when  the  fam- 


228  Heredity,  Disease  and  Human  Evolution 

ilies  of  both  parties  are  affected  with  the  same  disease.  As 
we  have  seen  (p.  175)  such  instances  are  by  no  means 
rare. 

The  identical  taint  is  especially  apt  to  be  present  on  both 
sides  when  we  have  to  do  with  the  blood-relations.  In 
such  eases,  therefore,  as  previously  explained  (p.  174)  es- 
pecial care  must  be  taken,  and  the  prohibition  of  marriage 
will  often  be  essential. 

Those  who  may  still  hesitate  to  prohibit  marriage  in  the 
cases  we  have  been  considering  should  call  to  mind  that 
there  are  also  social  reasons  for  such  a  step.  On  pecuniary 
and  ethical  grounds  it  may  seem  improbable  or  even  im- 
possible that  parents  affected  with  hereditary  disease  will 
be  able  to  provide  for  the  proper  upbringing  of  their  chil- 
dren. The  same  considerations  apply  to  those  suffering 
from  severe  tuberculosis.  Although  in  this  disease  inher- 
itance in  the  proper  sense  of  the  term  does  not  occur,  we 
cannot  expect  that  tuberculous  parents  will  be  able  to  pro- 
vide adequately  for  their  children's  education,  and  there 
also  exists  a  very  grave  danger  of  the  infection  of  the 
offspring  with  tubercle  bacilli  (see  p.  127).  For  these 
reasons  sufferers  from  well-marked  tuberculosis  should  not 
marry. 

What  are  we  to  do  meanwhile,  in  the  absence  of  appro- 
priate legislative  measures  ?  We  must  continue  to  promote 
the  widest  possible  discussion  of  the  problem  and  the  wid- 
est possible  diffusion  of  the  conclusions  to  which  that 
discussion  leads.  Much  would  be  gained  if  all  about  to 
marry  were  to  ask  themselves  whether  they  are  justified 
in  taking  such  a  step,  and  if  they  would  apply  for  expert 
advice.  The  idea  must  become  rooted  in  the  popular  con- 
sciousness that  no  one  should  marry  without  medical  ad- 
vice. Every  one  is  responsible  to  his  offspring,  and  he 
who  transmits  disease  to  his  descendants  acts  in  a  similar 
way  to  one  who  deliberately  infects  his  healthy  fellow  men 
with  disease,  to  one  who  injures  them  or  poisons  them.  It  is 
necessary  that  this  view  should  gain  ever  wider  acceptance. 


The  Abolition  of  Disease  229 

"We  may  then  hope  that  an  increasing  number  of  hered- 
itarily diseased  individuals  will  renounce  marriage,  or  that 
if  they  are  not  conscientious  and  intelligent  enough  to  do 
this,  they  will  be  constrained  by  their  relatives  and  by  the 
community-at-large.  Even  if  the  state  is  not  yet  prepared 
to  establish  marriage  prohibitions  for  diseased  individuals, 
it  should  at  least  give  zealous  and  thorough  support  to  all 
the  means  that  are  adapted  to  extend  our  knowledge  of 
heredity  in  general  and  of  the  inheritance  of  disease  in 
particular,  and  should  instruct  all  its  members  concerning 
the  dangers  and  wrongs  that  result  from  the  marriage  of 
individuals  affected  with  hereditary  disease.  On  the  other 
hand,  the  state  should  favour  in  every  possible  way  the 
marriage  of  healthy  individuals  and  the  procreation  of 
children  by  these.  This  is  a  matter  wherein  the  state  has 
a  high  direct  personal  interest,  for  the  community  is 
more  flourishing  in  proportion  as  the  number  of  the  sick 
is  small  and  the  number  of  the  healthy  large. 

If  it  be  the  duty  of  the  state  to  care  for  the  well  being 
of  its  members,  it  will  incur  blame  should  it  fail  to  do 
everything  in  its  power  to  restrict  the  procreation  of  dis- 
eased children. 


CHAPTER  X 

HOW  SHALL  WE  COME  TO  TERMS  WITH  DISEASE? 

In  all  our  activities  we  are  continually  subjected  to  the 
influence  of  disease,  either  because  we  are  ourselves  the 
sufferers,  or  because  our  fellows  are  affected,  and  we  are 
thereby,  as  previously  shown,  indirectly  implicated  in  one 
way  or  another.  The  injury  inflicted  on  our  race  by  dis- 
ease is  inconceivably  great.  It  interferes  enormously  with 
human  evolution.  Better  times  than  our  own,  times  in 
which  civilisation  will  attain  to  higher  levels,  and  in  which 
all  will  participate  in  its  advantages,  can  arrive  only  when 
disease  has  disappeared,  or  has  at  least  been  greatly  re- 
stricted in  extent.  From  such  a  future  we  are  still  far 
removed.  We  learned  in  the  previous  chapter  that  in  the 
prevention  of  individual  diseases  some  successes  have  al- 
ready been  gained.  But  on  the  whole  little  has  yet  been 
done,  and  as  far  as  the  prevention  of  hereditary  morbid 
conditions  is  concerned  we  stand  at  the  very  beginning  of 
our  task.  It  is  only  by  gradual  progress  that  we  can  hope 
to  attain  useful  results  in  this  direction,  through  a  clear 
insight  and  energetic  good-will  on  the  part  of  all,  or  at  any 
rate  on  the  part  of  all  persons  of  influence.  At  present 
these  conditions  are  unfulfilled,  and  even  were  it  other- 
wise we  could  not  count  upon  making  conspicuous  prog- 
ress within  any  reasonable  time.  Consequently,  our  race 
will  continue  for  a  long  period  to  suffer  from  disease,  and 
untold  future  generations  will  have  to  reckon  with  it. 

Can  we  hope  that  there  will  ever  be  any  change  in  this 
respect?  Are  we  justified  in  believing  that  in  some  remote 
epoch  of  human  history — so  remote  as  to  seem  of  little 

230 


How  Shall  We  Come  to  Terms?       231 

practical  concern — disease  will  altogether  disappear?  Is 
not  illness  a  necessary  and  inseparable  accompaniment  of 
the  evolution  of  the  whole  organic  world?  The  question 
was  discussed  in  the  eighth  chapter,  but  must  here  be 
reconsidered  in  somewhat  fuller  detail,  and  in  part  from 
a  different  outlook. 

Let  us  start  from  the  idea  of  evolution.  In  the  case  of 
living  organisms  this  involves  the  gradual  transformation 
from  the  most  simple  to  the  most  complex  types,  and  in- 
volves therewith  a  progress  to  higher  forms,  in  accompani- 
ment with  the  continued  development  of  the  mental  facul- 
ties. Evolution,  however,  also  signifies  the  formation  of 
the  worlds  in  which  organisms  live ;  it  signifies  further 
the  destruction  of  worlds  and  of  living  beings  and  the 
transition  to  other  forms.  Evolution  is  thus  the  continu- 
ous process  of  transformation  undergone  by  all  the  con- 
stituents of  the  universe.  Form  succeeds  form,  one  ever 
replacing  another,  in  accordance  with  unalterable  rules  and 
in  unending  succession.  Thus  the  universe  is  a  whole  in 
a  state  of  unceasing  flux,  and  everything  that  arises  does 
so  as  the  outcome  of  pre-existing  conditions.  The  universe 
is  the  sum  of  an  infinite  total  of  possibilities,  possibilities 
which  realise  themselves  in  the  process  of  evolution,  disap- 
pearing in  one  place  to  reappear  in  another. 

According  to  this  view,  the  world  is  not  a  chaos  in  which 
form  came  into  existence  out  of  a  formless  fermenting  sub- 
stance, but  rather  an  unceasing  succession  of  processes,  a 
persistent  change  of  forms,  associated  each  with  the  others 
by  an  inner  harmony.  The  world  is  not  a  chaos  but  a 
cosmos. 

Of  this  unceasing  formative  process  the  evolution  of  liv- 
ing organisms  upon  our  earth  (or  in  other  Avorlds  than 
ours)  constitutes  no  more  than  a  tiny  fraction.  Yet  this 
process  is  the  field  of  operation  of  innumerable  possibilities. 
The  multiplicity  of  successive  and  contiguous  forms  is  in- 
conceivably great,  but  the  transformations  of  all  these 
do   not  proceed   in   mutual    independence   for   they   are 


232  Heredity,  Disease  and  Human  Evolution 

closely  inter-related.  One  form  is  determined  by  another, 
and  by  the  rest  of  the  environment.  This  mutual  depend- 
ence is  not  merely  one  of  the  conditions  of  the  typical  proc- 
ess of  evolution,  inasmuch  as  in  the  development  of  new 
forms  there  occurs  an  adaptation  to  other  forms  and  to  the 
remaining  conditions  of  existence;  it  is  a  condition  also 
for  the  origination  of  diseases.  For  if  the  adaptation  to 
far-reaching  demands  prove  insufficient,  whether  these  de- 
mands proceed  from  non-living  factors  of  the  environ- 
ment, or  from  other  organisms  which  conflict  with  those 
whose  development  is  newly  proceeding,  it  results  that  the 
living  organisms  that  have  proved  incompetent  to  undergo 
adaptation  become  diseased  and  perish.  Thus  disease  is  a 
necessary  accompaniment  of  evolution. 

How  does  this  view  harmonise  with  the  idea  of  the  cos- 
mos? If  disease  exists  within  this  cosmos,  can  we  regard 
it  as  a  whole  which  evolves  always  harmoniously  and 
in  accordance  with  law?  At  first  sight  this  would  seem 
impossible,  but  as  we  attain  to  a  fuller  insight  the  appar- 
ent contradiction  disappears. 

It  is  evident  that  disease  does  not  involve  any  interrup- 
tion of  the  regular  succession  of  natural  phenomena  in 
accordance  with  invariable  law.  Morbid  processes  are 
just  as  plainly  subject  to  law  as  are  normal.  "When  a 
noxious  influence  affects  our  body,  the  consequences  of  its 
action  are  necessary  in  exactly  the  same  way  as  is  neces- 
sary, under  ordinary  conditions,  the  succession  of  any  phe- 
nomenon to  another.  To  the  world-all  it  is  a  matter  of 
perfect  indifference  whether  in  our  view  a  process  is 
morbid  or  normal. 

In  ourselves,  subject  as  we  are  to  narrow  limitations, 
disease  ensues  when  changes  are  induced  in  our  organs. 
The  organs  have  functions  indispensable  to  our  well-being, 
and  these  functions  cannot  be  disturbed  except  to  our 
detriment.  But  we,  who  are  thus  made  ill,  have  no  func- 
tions in  relation  to  the  world-all,  we  yield  it  nothing. 
Whether  we  are  ill  or  well  is  a  matter  of  importance  to  us, 


How  Shall  We  Come  to  Terms?       233 

but  not  to  the  cosmos,  whose  evolution  is  nowise  hindered 
by  the  fact  that  our  functional  activity  is  depressed,  that 
our  value  is  diminished,  or  that  we  perish  from  disease. 

It  follows  that  the  existence  of  disease  does  not  involve 
any  contradiction  with  our  idea  of  the  cosmos,  even  though 
we  are  compelled  to  regard  disease  as  necessarily  associated 
with  the  evolution  of  the  organic  world.  It  is  possible, 
however,  on  the  ground  of  this  necessary  association,  to 
raise  another  objection.  It  may  be  said  that  the  admis- 
sion that  the  association  is  necessary  involves  the  further 
admission  that  our  endeavours  to  abolish  disease  must  be 
vain,  for  how  can  we  abolish  what  is  necessary?  Morbid 
conditions  must  continue  so  long  as  organic  evolution  pro- 
ceeds. Is  this  conclusion  justified?  No,  for  disease  is  a 
regular  and  necessary  accompaniment  of  the  evolutionary 
process  only  in  the  case  of  those  organisms  that  are  not 
empowered  by  rational  thought  to  modify  the  conditions  of 
their  own  evolution.  Man  is  able  deliberately  to  regulate 
the  struggle  for  existence,  and  to  diminish  or  overcome  his 
dependence  upon  environmental  conditions.  Thus,  from 
a  theoretical  point  of  view  we  may  conclude  that  he  will 
ultimately  be  able  to  counteract  the  noxious  influences  that 
cause  disease,  and  thus  to  abolish  it.  It  is  true  that  he 
will  only  be  able  to  effect  this  very  gradually,  and  that 
the  end  will  be  completely  attained,  if  ever,  in  an  ex- 
tremely remote  future.  Yet  such  must  always  be  man's 
goal.  Not  until  our  race  is  freed  from  disease  will  it 
become  competent  for  its  highest  evolution. 

The  measures  men  adopt  in  their  attempts  to  abolish 
disease  are  not  matters  of  arbitrary  choice.  As  we  have 
previously  explained,  the  struggle  with  pathological  states 
is  a  necessary  product  of  human  evolution.  By  an  inward 
impulse  man  is  forced  to  fight  against  disease.  This  reac- 
tion on  his  part  is  just  as  necessary  as  has  been  the  orig- 
ination of  disease  as  an  outcome  of  evolutionary  conditions. 
Very  slowly,  however,  will  this  necessary  struggle  prove 
successful. 


234  Heredity,  Disease  and  Human  Evolution 

For  a  long  time  to  come  we  shall  have  to  reckon  with 
the  existence  of  diseases,  and  the  question  therefore  arises, 
^ow  we  are  to  come  to  terms  with  them  until  that  remote 
day  dawns  when  we  may  hope  for  their  abolition.  Would 
it  give  us  adequate  satisfaction  if,  through  our  energetic, 
campaign  against  disease,  though  we  should  gain  very  little 
for  ourselves,  we  might  perhaps  secure  more  favourable 
conditions  for  later  generations?  This  question  must  cer- 
tainly be  answered  in  the  negative.  It  may  interest  us 
theoretically  to  know  how  our  offspring  in  distant  times 
will  fare  as  regards  health,  but  such  knowledge  cannot 
help  us  through  our  own  troubles.  Speaking  generally 
it  may  be  said  that  it  is  useless  to  attempt  to  console  those 
who  are  unhappy  in  the  present  by  assuring  them  that 
their  offspring  will  some  day  be  happier.  However  much 
we  may  discuss  the  possibility  of  human  advance  towards 
a  higher  and  better  civilisation,  however  certain  such  an 
advance  may  appear,  no  one  to-day  will  for  this  reason  be 
rendered  in  the  least  happier  than  he  is.  The  first  de- 
mand of  human  beings  is  to  be  satisfied  with  the  conditions 
of  their  personal  existence.  They  think  always  of  them- 
selves first,  then  of  their  near  relatives,  then  of  more 
distant  kin,  then  of  acquaintances,  of  their  other  asso- 
ciates, of  their  fellow-countrymen.  The  state  of  civilisa- 
tion to  be  attained  by  remote  posterity  is  of  merely  theo- 
retical interest,  and  its  contemplation  can  exercise  but 
little  influence  on  those  now  alive. 

In  these  circumstances  we  have  to  ask  how  we  may  best 
come  to  terms  with  the  diseases  that  now  exist.  This  is 
the  crux  of  the  problem.  We  are  not  yet  able  to  abolish 
them,  so  how  can  we  live  with  them?  Is  it  possible  for 
us,  disease  notwithstanding,  so  to  arrange  our  lives  as  to 
find  full  satisfaction?  What  steps  can  we  take  towards 
this  goal?  Our  first  aim  will  naturally  be  an  endeavour 
to  ensure  that  the  curable  diseases  shall  run  a  favourable 
course.  Next  we  must  try  to  mitigate  as  far  as  possible 
the  consequences  of  illness.    In  this  respect  much  can  al- 


How  Shall  We  Come  to  Terms?       235 

ready  be  done.  By  appropriate  medical  measures  we  lessen 
the  bodily  troubles  which  are  the  sequels  of  diseases  that 
have  been  but  imperfectly  cured ;  persons  permanently 
invalided  by  illness,  if  they  lack  private  means,  are  cared 
for  in  infirmaries  and  asylums;  through  social  legislation, 
such  as  the  system  of  national  insurance,  we  take  steps  to 
provide  compensation  for  those  who  have  been  partially 
or  wholly  incapacitated  for  work.  Thus  suffering  is  avoided 
which  in  former  times  was  inevitable.  Yet  there  still 
remains  much  poverty  dependent  upon  mental  or  physical 
incapacity  for  work — poverty  which,  though  preventable,  is 
not  prevented  by  the  measures  now  in  force.  To  provide 
more  adequate  help  in  this  respect  is  the  duty  of  the  state 
and  of  the  community  at  large. 

Apart  from  these  measures,  we  must  take  steps  to  obviate 
the  consequences  entailed  by  disease  in  the  religious  do- 
main, consequences  which  find  expression  in  that  dogmatic 
intolerance  whose  disadvantageous  influence  upon  the 
course  of  human  evolution  it  is  hardly  possible  to  over- 
estimate. This  intolerance,  which  exists  solely  because  of 
disease,  must  be  restrained  by  all  the  means  in  our  power. 
But  the  task  is  not  an  easy  one.  Dogma  being  essentially 
intolerant,  intolerant  also  are  an  extraordinarily  large  pro- 
portion of  its  adherents.  It  is  difficult  or  impossible  to 
convince  the  dogmatist  that  other  views  than  his  own  have 
also  a  right  to  exist.  Yet  it  is  precisely  the  dogmatist  who 
should  be  accessible  to  such  an  idea.  For  those  whose 
dispositions  are  truly  religious  feel  that  their  views  spring 
from  their  own  inner  natures,  and  they  ought  to  be  willing 
to  admit  that  the  ideas  of  others  well  up  with  the  like  ir- 
resistible force  from  within — and  that  others,  like  them- 
selves cleave  to  their  own  views  from  profound  conviction, 
and  cannot  do  otherwise.  Few  adherents  of  dogma,  how- 
ever, are  capable  of  recognising  this,  and  hence  the  sup- 
pression of  intolerance  is  as  difficult  as  it  is  indispensable. 
Even  to-day,  notwithstanding  the  existence  of  disease,  life 
would  be  far  more  satisfactory  and  much  happier  if  every 


236  Heredity,  Disease  and  Human  Evolution 

one  were  willing  to  allow  every  one  else  to  be  happy  after 
his  own  fashion. 

To  do  away  with  the  consequences  of  disease  is  a  merely 
negative  task.  A  matter  of  far  greater  importance  is  for 
men  to  search  for  that  which  is  healthy  in  themselves  and 
their  fellows,  and  to  foster  this  in  every  possible  way — to 
seek  the  healthy,  which  is  alone  worth  while,  which  cor- 
responds to  his  innermost  sentiments,  which  he  greets 
wherever  he  finds  it.  Disease,  on  the  other  hand,  which 
men  instinctively  dislike,  which  thej'-  regard  as  disagree- 
able, antipathetic,  and  uncanny,  must  not  be  allowed  to 
gain  a  wider  sphere  of  influence  than  it  possesses  to-day. 
On  the  contrary,  disease  must  be  repressed.  Man  must 
learn  to  recognise  clearly  that  disease  is  not  a  permanent 
and  essential  part  of  his  nature,  that  morbidity,  however 
closely  it  attaches  to  the  individual  and  unfits  him  for 
functional  activity,  is  merely  imposed  upon  the  race  as  a 
whole,  and  therefore  of  course  upon  the  individual,  by 
certain  external  conditions,  is  no  more  than  an  accidental 
attribute.  We  could  conceive  disease  as  non-existent  with- 
out mankind's  thereby  suffering  any  loss.  The  idea  of 
humanity,  if  we  may  use  this  term  to  make  our  meaning 
clear,  traverses  the  whole  of  its  evolution,  unchanged  by 
disease,  although  assuredly  progress  is  hindered  by  the 
existence  of  disease.  The  idea  of  humanity  connotes  also 
the  idea  of  health.  All  that  exists  in  the  individual  in  the 
way  of  normal  elements,  apart  from  disease  and  abnor- 
mality of  constitution,  is  summed  up  in  the  human  race 
as  a  whole  to  form  the  concept  of  the  healthy  human  being, 
of  one  whose  development  is  all-sided,  harmonious  in  body 
and  in  mind,  and  harmonious  also  in  functional  activity. 
Not  thus  do  we  know  man  to-day,  but  thus  we  imagine 
him  in  the  remote  future.  With  Nietzsche  we  hope  for  the 
coming  of  more  highly  evolved  human  beings.  What  Neitz 
sche  speaks  of  as  the  superman  is  in  our  sense  the  healthy 
human  being  in  the  plenitude  of  his  powers,  all  of  whose 
faculties  are  developed  to  the  full,  who  no  longer  knows 


How  Shall  We  Come  to  Terms?       237 

anything  of  sympathy  merely  because  there  no  longer 
exists  anything  to  arouse  it,  and  who  is  beyond  good  and 
evil  because  there  will  no  longer  be  any  place  for  these 
ideas  as  now  understood.  Evil  is  merely  the  outcome  of 
man's  morbid  state.  The  healthy  human  being  knows  noth- 
ing of  evil  because  he  is  capable  of  no  other  actions  than 
those  that  are  good,  that  is  to  say,  in  harmony  with  the 
aims  of  human  evolution.  To-day,  indeed,  man  knows 
evil,  but  only  because  he  sees  it  in  diseased  and  abnormal 
individuals.  If  at  some  future  date  disease  should  cease 
to  exist,  there  will  no  longer  be  any  evil. 

Man's  desires  are  therefore  set  upon  the  attainment  of 
this  state  of  perfect  health.  It  is  one  at  which  he  cannot 
hope  to  arrive  for  long  ages  yet  to  come,  and  his  longing 
for  it  cannot  now  be  appeased.  At  present,  and  until  the 
aims  of  racial  hygiene  are  fulfilled,  diseases  must  continue 
to  prevail,  with  all  their  destructive  consequences.  Thus 
the  only  choice  open  to  us  is  to  oppose  disease  to  the  best 
of  our  ability,  to  foster  health  and  develop  it  to  the  utmost 
of  our  powers.  We  must  take  steps  to  secure  that  disease 
shall  not  thrust  itself  into  the  foreground  and  determine 
our  views  of  life.  Regarding  it  as  something  foreign-  to 
our  nature,  we  must  always  and  everywhere  repress  its 
manifestations. 

The  man  whose  thoughts  are  healthy  must  discover  the 
healthy  sides  of  his  own  individuality,  must  cultivate  and 
favour  these,  and  thus  make  the  content  of  his  existence  as 
rich  as  possible.  For  this  the  various  sides  of  his  ego  pro- 
vide him  with  manifold  and  fruitful  opportunities.  Ac- 
cording to  the  nature  of  his  tendencies  he  can  develop  one 
or  all  of  these,  and  allow  those  of  them  to  gain  dominion 
whereby  the  morbid  elements  will  be  repressed,  and  will  no 
longer  exercise  a  determinative  influence  upon  the  content 
of  existence. 

Among  the  healthy  activities  of  our  race  the  most  impor- 
tant is  the  pursuit  of  knowledge,  which  finds  expression  in 
our  scientific  work  considered  as  a  whole.    Little  by  little, 


238  Heredity,  Disease  and  Human  Evolution 

man  unveils  the  secrets  of  nature,  and  the  smallest  gain  in 
this  direction  secures  for  him  the  highest  and  purest  pleas- 
ure. Even  those  who,  although  they  do  not  themselves 
actively  participate  in  this  work,  are  privileged  to  share 
an  understanding  of  its  results,  gain  thereby  the  greatest 
satisfaction.  It  is  not,  however,  the  small  and  individual 
results  which  especially  please  us.  The  full  value  of  these 
separate  items  depends  upon  the  fact  that  they  serve  for 
the  foundation  of  general  ideas,  affording  fresh  means  for 
the  interpretation  of  the  great  interconnexions  of  things, 
a  fuller  understanding  of  the  relationship  of  humanity 
to  the  universe.  All  the  detailed  progress  effected  in  any 
particular  science,  be  it  natural  science  or  history,  be  it 
linguistic  science  or  medicine,  acquires  its  full  significance 
only  when  it  enhances  our  insight  into  the  universe.  This 
is  the  knowledge  we  so  ardently  desire.  By  means  of  such 
knowledge  we  draw  nearer  to  the  great  whole,  we  feel 
more  and  more  that  we  belong  to  that  whole,  that  we  are 
parts  of  the  infinitely  great.  We  thus  derive  a  profound 
inward  satisfaction. 

In  this  insight  there  is  contained  a  well-marked  religious 
factor.  For  religion  really  signifies  nothing  more  than  the 
feeling  of  our  affinity  to  the  universe,  and  not,  as  it  has 
sometimes  been  defined,  the  feeling  of  dependence,  which 
can  never  have  a  religious  character.  Dependence  arouses 
embarrassment,  discomfort,  envy,  dread,  and  hatred.  The 
dependent  feels  depressed,  and  never  rejoiced,  by  his  condi- 
tion. Affinity,  on  the  other  hand,  arouses  confidence,  a 
sense  of  security  and  elevation.  The  feeling  that  we  be- 
long to  a  family,  to  a  nation,  to  a  state,  makes  us  happy 
and  proud.  This  feeling  gives  to  the  individual  a  sense  of 
being  protected.  The  man  who  seeks  inward  peace  takes 
refuge  with  his  own,  with  those  to  whom  he  belongs.  When 
the  believer  honours  God  as  his  father,  and  feels  himself 
to  be  God's  child,  what  does  this  signify  other  than  his 
conviction  that  he  belongs  to  God !  It  is  true  that  the 
feeling  is  here  also  associated  with  one  of  dependence,  but 


How  SliaU  We  Come  to  Terms?       239 

this  latter  does  not  constitute  the  essence  of  the  idea  of 
the  filial  relationship,  which  can  arise  only  out  of  a  sense 
of  affinity.  The  child  feels  secure  in  the  family,  only  be- 
cause it  is  of  one  nature  with  its  parents,  because  it  belongs 
to  them. 

The  scientific  thinker's  sense  of  affinity  to  the  universe 
thus  contains  a  religious  element,  which  can  find  pure  ex- 
pression only  in  the  healthy  individual,  or,  to  word  it  bet- 
ter, only  in  a  healthy  humanity.  He  knows  that  he  derives 
from  the  cosmos,  and  that  into  this  he  will  merge  once 
more,  to  be  taken  up  afresh  into  the  unending  course  of 
evolution.  This  is  a  religious  idea,  but  it  is  one  in  which 
mankind  will  not  fijid  complete  satisfaction  until  the  mem- 
bers of  our  race  are  all  perfectly  healthy,  until  their  lives 
are  therefore  perfectly  happy,  and  until  death  comes  solely 
through  the  gradual  onset  of  old  age. 

The  acquirement  of  knowledge  is  therefore  the  most  im- 
portant means  by  which  we  are  enabled  to  oppose  morbid 
conditions,  to  forget  them,  or  to  render  them  less  percepti- 
ble. An  additional  help,  however,  is  derivable  from  the 
pure  enjoyment  of  the  unspeakable  beauties  which  the 
world  offers  to  our  contemplation.  The  beauties  of  nature 
affect  man  profoundly.  He  merges  himself  in  these  beau- 
ties, feels  akin  to  them,  sees  in  all  that  lives  and  all  that 
exists  an  image  of  his  own  being,  just  as  in  himself  he  sees 
an  image  of  the  whole.  It  is  only  because  he  has  assurance 
of  this  essential  identity  that  he  is  able  to  merge  himself 
wholly  in  nature  and  to  give  himself  up  unreservedly  to 
its  enjoyment.  The  infinitely  little  and  the  inconceivably 
great,  the  inorganic  crystal  as  well  as  all  the  vital  proc- 
esses of  the  organic  world,  the  organisation  of  plants  and 
of  animals,  the  art-forms  of  nature  (as  Haeckel  terms 
them) — all  these  things  afford  ever-renewed  sources  of 
delight.  But  man  must  be  receptive  for  these  beauties  and 
this  he  can  be  to  the  full  only  when  he  is  healthy,  or  at  least 
when  he  can  make  himself  independent  of  disease.  The 
majority  of  invalids,  those  who  are  mentally  abnormal, 


240  Heredity,  Disease  and  Human  Evolution 

those  whose  development  is  one-sided,  pass  by  the  beauties 
of  nature  without  regarding  or  comprehending  them,  A 
general  and  joyful  appreciation  of  nature  will  become  pos- 
sible solely  through  the  disappearance  of  disease. 

Happiness  is  derived  also  from  the  beauties  of  art.  How 
profound  the  inner  satisfaction,  how  complete  the  libera- 
tion from  the  pressing  cares  of  everyday  life,  afforded  by 
the  appreciation  of  music,  poetry,  painting,  and  sculpture 
— to  this  countless  healthy  human  beings  can  bear  witness. 
We  forget  the  surrounding  world,  we  experience  the  domi- 
nance of  beauty,  and  are  rejoiced.  But  for  this  to  be  pos- 
sible there  must  also  exist  a  suitable  capacity,  a  receptive 
faculty.  Many  invalids  and  abnormal  human  beings  are 
unable  to  find  pleasure  in  any  branch  of  art.  Here  im- 
provement can  be  effected  only  by  the  general  diffusion  of 
health.  Then  the  joys  of  eesthetic  pleasure  will  become 
more  widely  disseminated,  those  joys  which  all  that  finds 
expression  in  art  yields  to  the  most  intimate  nature  of  man. 

A  manifold  source  of  satisfaction  is  also  found  by  human 
beings  in  the  process  of  absorption  into  the  lives  of  their 
healthy  fellows.  The  example  of  great  men,  healthy  in 
their  greatness,  is  elevating,  and  to  follow  the  mental  life 
of  leading  individuals  in  their  spoken  or  printed  experi- 
ences may  be  a  source  of  the  highest  pleasure.  To  become 
acquainted  with  a  significant  human  being,  one  harmoni- 
ously self-sufficient,  functionally  capable,  embracing  hu- 
manity and  the  universe  in  his  comprehensive  thought,  may 
furnish  enduring  happiness. 

We  think  here  not  only  of  our  contemporaries.  The 
great  and  healthy  individualities  of  the  past,  those  of  an 
earlier  epoch  however  remote,  may  liberate  our  spirits  and 
enable  us  to  forget  our  morbid  condition.  The  historical 
evolution  of  our  race  affects  us  in  the  same  way.  We  feel 
it  to  be  something  beautiful  and  great  to  merge  ourselves 
in  imagination  in  the  being  and  the  activities  of  earlier 
generations  and  in  all  the  healthy  results  that  human  effort 
has  effected  in  every  domain.    The  meaning  of  humanity  is 


How  Shall  We  Come  to  Terms'?       241 

found  only  in  humanity  as  a  whole.  One  who  confines  his 
attention  to  the  life  of  to-day  learns  but  a  small  fragment. 
For  this  reason,  the  study  of  history  is  one  of  the  most 
important  occupations  of  healthy  humanity. 

The  reflective  man  gains  satisfaction,  not  merely  when 
he  prepares  for  his  fellows  the  pleasures  of  knowledge,  na- 
ture, and  art,  but  also,  and  often  to  a  greater  extent,  when 
he  reveals  these  pleasures  to  others.  Healthy  and  healthy- 
minded  human  beings  feel  that  they  are  inter-related,  that 
they  belong  to  one  another,  that  they  are  members  of  a 
greater  whole.  As  Kropotkin  has  shown  in  his  instructive 
work  on  Mutual  Aid,  the  lower  animals  of  the  same  species 
hold  together  and  give  one  another  mutual  support. 
Healthy  human  beings  do  the  same,  whereas  those  who  are 
diseased,  dogmatists,  one-sided  persons,  egoists,  and  jin- 
goes, make  war  upon  one  another.  The  individual  knows 
that  he  cannot  permanently  live  for  himself  alone.  Mutual 
aid  is  essential  to  the  success  of  individuals  no  less  than  to 
that  of  humanity  as  a  whole.  The  happiness  of  one  is 
incomplete  without  the  happiness  of  all.  How  can  any  one 
feel  well  when  he  has  to  witness  the  suffering  of  his  near 
associates  or  of  his  fellow-countrymen?  None  but  the 
egoist  can  be  satisfied  under  such  conditions.  To  him  it 
matters  not  if  others  be  ill,  so  long  as  he  is  well.  But 
egoism  is  one-sidedness,  is  an  anomaly,  is  morbid.  The 
healthy  individual  is  interested  in  his  family,  in  his  friends, 
in  his  country,  and  is  ready  to  sacrifice  himself  for  these. 

Out  of  this  feeling  of  the  mutual  affinity  of  human  beings 
there  arises  the  care  for  others'  weal,  altruism,  social  activ- 
ity. To  render  help  to  others  is  a  source  of  purest  joy  to 
all  whose  sentiments  are  not  distorted  by  disease  or  other 
abnormality.  The  necessity  of  social  effort  will,  however, 
certainly  diminish  in  proportion  as  mankind  becomes  more 
healthy,  for  this  necessity  depends  solely  upon  the  fact  that 
most  human  beings  are  abnormal,  being  in  part  diseased 
in  the  narrower  sense  of  the  term,  and  in  part  below  par- 
value,  and  ill  adapted  for  the  struggle  for  existence.    In 


242  Heredity,  Disease  and  Human  Evolution 

a  healthy  human  race,  altruistic  activity  would  no  longer 
be  essential. 

To-day,  however,  the  need  for  altruism  exists.  It  must 
be  our  aim,  not  only  to  diminish  the  outward  and  physical 
suffering  of  others,  but  also  to  awaken,  to  cultivate,  and 
to  develop  all  that  in  them  is  mentally  healthy.  One  of 
the  principal  duties  of  healthy  men  is  to  allow  others  to 
share  to  the  extent  that  their  understandings  permit  in 
all  that  they  themselves  effect  or  are  interested  in  in  science, 
natural  knowledge,  and  art. 

Those  whose  mental  values  are  defective,  and  above  all 
those  whose  powers  and  opportunities  have  been  restricted 
by  poverty,  must  receive  their  share  in  the  mental  treasures 
of  healthy  humanity,  which  alone  bring  true  happiness.  A 
great  injustice  is  committed  if  no  steps  are  taken  to  secure 
for  those  who  have  to  earn  their  daily  bread  by  arduous 
labour  some  share  of  that  which  is  offered  to  others  in 
abundance,  some  of  the  happiness  which  art  and  science 
can  yield.  People  complain  of  the  roughness,  the  laziness, 
and  the  lack  of  interest  of  the  industrial  and  agricultural 
workers,  and  deplore  the  ravages  of  alcoholism.  But  such 
complaints  lack  justification  if  no  opportunity  is  provided 
for  human  beings  to  employ  their  good  qualities  and  to 
strengthen  these  by  exercise,  while  repressing  their  un- 
desirable tendencies.  We  shall  succeed  very  imperfectly  in 
freeing  people  from  the  scourge  of  alcoholism  by  endeavour- 
ing to  instruct  them  as  to  the  dangers  of  alcohol.  They 
lack  the  insight  necessary  to  understand  these  dangers,  and 
this  insight  can  develop  only  as  their  condition  becomes 
more  healthy.  In  the  weaning  of  men  from  alcohol  we 
cannot  expect  to  attain  to  satisfactory  results,  unless  we 
provide  for  them  a  liberation  from  the  cares  and  burdens 
of  every-day  life — a  liberation  they  now  seek  and  find  in 
alcohol — by  providing  them  with  intellectual  enjoyments. 
Nor  can  we  cure  their  roughness  in  any  other  way  than 
this.  It  is  true  that  we  must  not  nourish  exaggerated 
hopes.    Alcoholism  and  roughness  are  for  the  most  part  the 


How  ShaU  We  Come  to  Terms?       243 

outcome  of  a  morbid  mental  constitution,  and  will  disap- 
pear with  this  constitution  in  subsequent  generations,  when 
we  succeed  in  effecting  the  sanation  of  our  race.  Still,  we 
may  always  hope  that  by  such  measures  as  are  here  sug- 
gested we  shall  strengthen  and  cultivate  the  healthy  men- 
tal sides  of  those  to  whom  they  are  applied,  and  that  not 
infrequently  in  such  cases  the  healthy  will  get  the  upper 
hand  of  the  morbid. 

In  such  cares  for  the  mental  culture  of  his  fellows  the 
reflective  man  finds  a  further  source  of  profound  satisfac- 
tion which  will  assist  him  to  ignore  disease  in  himself  and 
in  others. 

Another  important  point  has  to  be  considered.  No  one 
can  be  equally  active  in  all  directions  at  once.  Most  indi- 
viduals are  more  highly  gifted  in  some  particular  sphere. 
This  indicates  to  us  a  very  important  task,  namely,  to  de- 
velop to  the  full  the  special  gift,  while  avoiding  the  pro- 
duction of  an  injurious  one-sidedness — to  cultivate  to  the 
utmost  the  special  faculty,  whatever  it  may  be,  scientific, 
artistic,  or  social.  Any  one  who  feels  at  home  in  any  par- 
ticular domain,  who  in  this  domain  can  excel  or  can  at 
any  rate  effect  much,  will  derive  especial  pleasure  from  the 
exercise  of  this  pre-eminent  faculty,  and  even  if  he  be 
ailing  will  be  lifted  by  such  exercise  above  his  personal 
troubles.  Not  until  each  individual  can  develop  his  pecul- 
iar talents  to  the  full,  can  humanity  as  a  whole  advance 
as  it  should.  One  of  the  most  important  aims  of  education, 
as  Ostwald  has  shown,  is  to  favour  the  growth  of  individu- 
ality, to  recognise  greatness  early,  and  to  cultivate  it. 

Thus  for  the  reflective  man  there  exist  numerous  possi- 
bilities aided  by  which  he  will  rise  superior  to  the  existence 
of  diseases,  notwithstanding  the  enormous  amount  of  in- 
jury these  inflict  upon  mankind.  Inasmuch  as  he  is  con- 
vinced that  disease  is  a  force  hostile  to  his  nature,  he  will 
strive  to  attain  perfect  health,  and  will  hope  that  our  race 
as  a  whole  will  some  day  acquire  this  also,  though  in  a 
remote  future.    But  as  long  as  disease  continues  to  exist, 


244  Heredity,  Disease  and  Human  Evolution 

he  must  do  his  best  to  counteract  the  consequences  entailed 
by  disease  in  the  physical  and  mental  sphere,  must  culti- 
vate and  develop  the  healthy  elements  which  exist  ia  indi- 
viduals in  varying  degree,  and  as  the  outcome  of  these 
endeavours  must  gain  the  energy  that  will  enable  him  to 
thrust  into  the  background  those  disquieting  and  painful 
hindrances  to  life  which  are  now  dependent  upon  the  ex- 
istence of  disease. 

Health  remains  the  desire  arid  the  goal  of  humanity.  In 
the  desire  for  health  all  other  desires  are  comprised ;  in  the 
attainment  of  health  the  satisfaction  of  all  other  desires  is 
promised.  The  healthy  man  is  in  harmony  with  his  own 
being,  in  harmony  with  the  healthy  human  race,  and  in 
harmony  with  the  universe.  Health  is  happiness,  the  great 
happiness  for  which  man  yearns.  If,  as  we  are  often  as- 
sured, the  aim  of  humanity  must  be  to  secure  the  greatest 
good  of  the  greatest  number,  this  good  will  certainly  be 
attained  with  the  attainment  of  general  health.  This  is  the 
end  of  every  man's  desire. 


THE  END 


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BIRTH  CONTROL 

—  OR ! 

The  Limitation  of  Offspring  by 
the  Prevention  of  Conception 

BY 

WILLIAM  J.  ROBINSON,  M,D. 

With  an  Introducttott  by  , 

A.  JACOBI,  M.D.,  LL.D. 

3x-Prtsident  of  The  American  Medical  AssociatUm 

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The  Limitation  of  Offspring  is  now  the  burning 
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ception when  necessary.  For  many  years  he  fought 
practically  alone;  his  propaganda  has  made  hundreds  of 
thousands  of  converts — now  the  ground  is  prepared  and 
the  people  are  ready  to  listen. 

Written  in  plain  popular  language.  A  book  which 
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A  few  of  the  subjects  which  the  author  discusses 
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The  Relations  Between  the  Sexes  and  Man's  Inhumanity 
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Health  and  Sexual  Power.  —  The  Double  Standard  of  Morality 
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ment of  the  Human  Race,  from  an  Economic  and  Eugenic 
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'* SEXUAL  PROBLEMS  OF  TO-DAY"  will  give 
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The  simple  practical  points  contained  in  its  pages 
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Certain  single  chapters  or  even  paragraphs  are  alone 
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From  Dr.iWilliam  J.  Robinson's  Introduction. 

The  Sexual  Crisis 

A  CRITIQUE  OF  OUR  SEX  LIFE 
A  Psychologic  and  Sociologic  Study 
By   GRETE    M  Ei  SEL- H  ESS 

AUTHORIZED  TRANSLATION  BY  EDEN  AND  CEDAR  PAUL 
EDITED,  WITH  AN  INTRODUCTION 

By   WILLIAM   J.    ROBINSON,    M.  D. 


One  of  the  greatest  of  all  books  on  the  sex  question 
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keen  analysis  of  the  conditions  which  are  bringing  about 
a  sexual  crisis,  the  book  abounds  in  gems  of  thought  and 
in  pearls  of  style  on  every  page.  It  must  be  read  to  be 
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Absolutely  free  from  any  cant,  hypocrisy,  falsehood, 
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6ook. 

Every  one  of  the  tales  teaches  a  distinct  lesson,  a  lesson  of  vital 
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"I  would  have  given  a  good  part  of  my  fortune  if  the  knowledge 
I  obtained  from  one  of  j>our  stories  to-day  had  been  imparted  to 
me  ten  years  ago." 

Another  one  writes: 

"I  agree  with  you  that  your  plain,  unvarnished  tales  from  real 
life  should  have  been  told  long  ago.  But  better  late  than  never. 
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EUGENICS,  MARRIAGE 

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BIRTH  CONTROL 

[Practical  Eugenics] 
By  WILLIAM  J.  ROBINSON,  M.D. 

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heredity  and  to  the  questions:  How  can  we  im- 
prove the  human  stock,  and  who  should  and 
should  not  marry  ?  These  practical  questions 
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UNCONTROLLED   BREEDING 

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FECUNDITY    vs.    CIVILIZATION 

A  contribution  to  the  study  of  over-population  as  the  cause 
of  War  and  the  chief  obstacle  to  the  Emancipation  of  Women 

By  ADELYNE  MORE 

With  an  Introduction  by  Arnold  Bennett  and  Preface  and 

Notes  by  William  J.  Robinson,  M.D. 

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One  of  the  greatest  books  on  Birth-Control  in 
the  EngHsh  or  any  other  language.  By  writers 
of  international  reputation. 

CONTENTS 

Introduction,  by  William  J.  Robinson;  Malthus,  a  Biographical 
and  Critical  Study,  by  Achille  Locia;  Birth-Control  and  the  Wage 
Earners,  by  Charles  V.  Drysdale;  Race  Suicide  in  the  United 
States,  by  Ludwig  Quessel;  Eugenics,  Birth-Control,  and  Social- 
ism, by  Eden  Paul;  Economics  of  the  Birth  Strike,  by  Ludwig 
Quessel;  Decline  in  the  Birth-Rate,  Nationality,  and  Civilisation, 
by  Edward  Bernstein;  Philosophy  of  the  Birth  Strike,  by  Ludwig 
Quessel;  Over-Population  as  a  Cause  of  War,  by  B.  Dunlop;  The 
Decline  in  the  Birth-Rate,  by  R.  Manschke;  Dysgenic  Tendencies 
of  Birth-Control  and  of  the  Feminist  Movement,  by  S.  H.  Halford; 
Women  and  Birth-Control,  by  F.  W.  Stella  Browne ;  Editorial  Sum- 
mary and  Conclusion. 

Price  $3.00 

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BIRTH-CONTROL  FROM  THE  MORAL, 
RACIAL  AND  EUGENIC  STANDPOINT 

BY 

Dr.  C.  V.  DRYSDALE 

DR.  HAVELOCK  ELLIS 

DR.  WILLIAM  J.  ROBINSON 

PROFESSOR  A.  GROTJAHN 

PHce  m^ee    /'  ro 

■  -  ADDRESS    •       '  = 

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SEX  MORALITY 

PAST,  PRESENT  AND  FUTURE 

Will  monogamy  or  variety  prevail 
in  the  future  ? 

Is  continence  injurious  ? 

Are  extra  -  marital  relations  ever 
justifiable  ? 

Should  there  be  one  moral  stand- 
ard for  men  and  women  ? 

Will  our  present  moral  code  persist? 

These  and  similar  questions  are  here  discussed 
by  original  and  unbiased  thinkers  as  well  as  by 
orthodox  conservatives.  No  matter  what  your 
opinion  on  the  subject  may  be,  no  matter  whether 
your  ideas  on  the  relations  of  the  sexes  are  those 
of  the  1  5  th,  20th  or  25  th  century,  you  should 
read  this  book.  Nobody  who  is  earnestly  inter- 
ested in  the  sex  question  has  a  right  to  have  any 
opinion  on  it  without  having  read  this  volume,  the 
price  of  which,  in  cloth»  is  $1;^  including  postage. 

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A  PRACTICAL  TREATISE  ON 

THE  CAUSES,  SYMPTOMS  AND 

TREATMENT    OF 
SEXUAL  IMPOTENCE 

And  Other  Sexual  Disorders  in  Men  and  Women 

BY 

WILLIAM  J.  ROBINSON,  M.D. 

Chief  of  the  Department  of  Genito-Urinary  Diseases  and  Dermatology, 

Bronx  Hospital  and  Dispensary;  Editor  The  American  Journal 

of  Urology,  Venereal  and  Sexual   Diseases;  Editor  and 

Founder  of  The  Critic  and  Guide;  Author  of  Sexual 

Problems   of  Today;     Never   Told   Tales; 

Practical   Eugenics,   etc. 

BRIEF  SYNOPSIS  OF  CONTENTS. 

Part  I — Masturbation.  Its  Prevalence,  Causes,  Varieties,  Symptoms, 
Ecsults,  Prophylaxis  and  Treatment.  Coitus  Interruptus  and  its 
ECects. 

Part  II — Varieties,  Causes  and  Treatment  of  Pollutions,  Spermator- 
rhea, Prostatorrhea  and  Urethrorrhea. 

Fart  III — Sexual  Impotence  in  the  Male.  Every  phase  of  its  widely 
varying  causes  and  treatment,   with  illuminating  case  reports. 

Part  IV — Sexual  Neurasthenia.  Causes,  Treatment,  case  reports, 
and  its  relation  to  Impotence. 

Part  V — Sterility,  Male  and  Female.     Its  Causes  and  Treatment. 

Part  VI — Sexual  Disorders  in  Woman,  Including  Frigidity,  Vaginis- 
mus, Adherent  Clitoris,  and  Injuries  to  the  Female  in  Coitus. 

Part  VII — Priapism.     Etiology,   Case  Eeports  and  Treatment. 

Part  VIII — Ivliscellaneous  Topics.  Including:  Is  Masturbation  a 
Vice? — Two  Kinds  of  Premature  Ejaculation. — The  Frequency  of 
Coitus. — "Useless"  Sexual  Excitement. — The  Relation  Between  Mental 
and  Sexual  Activity. — Big  Families  and  Sexual  Vigor. — Sexual  Per- 
versions. 

Part  IX — Prescriptions  and  Minor  Points. 

Third  edition  revised  and  enlarged. 

Cloth  bound,  422  pages.  Postpaid,  SStBB.  ^'  o  i 

THE  CRITIC  AND  GUIDE  COMPANY 

12  MT.  MORRIS  PARK  W.  NEW  YORK  CITY 


A  UNIQUE  JOURNAL 
THE 

CRITIC  AND  GUIDE 

Dr.  RoDinson  s  Famous  Little  Montnly 


It  is  the  most  original  journal  in  the  country.  It  is  the  only- 
one  of  its  kind,  and  is  interesting  from  cover  to  cover.  There  is  no 
routine,  dead  matter  in  it.  It  is  one  of  the  very  few  journals 
that  is  opened  with  anticipation  just  as  soon  as  it  is  received  and 
of  which  every  line  is  read  with  real  interest. 

Not  only  are  the  special  problems  of  the  medical  profession  itself 
dealt  with  in  a  vigorous  and  progressive  spirit,  but  the  larger,  social 
aspects  of  medicine  and  physiology  are  discussed  in  a  fearless  and 
radical  manner. 

Many  problems  untouched  by  other  publications,  such  as  the  sex 
question  in  all  its  varied  phases,  the  economic  causes  of  disease  and 
other  problems  in  medical  sociology,  are  treated  boldly  and  freely 
from  the  standpoint  of  modern  science.  In  discussing  questions 
which  are  considered  taboo  by  the  hyper-conservative,  the  editor 
says  what  he  wants  to  say  very  plainly  without  regard  for  Mrs. 
Grundy. 

The  Critic  and  Guide  was  a  pioneer  in  the  propaganda  for 
birth  control,  venereal  prophylaxis,  sex  education  of  the  young,  and 
free  discussion  of  sexual  problems  in  general.  It  contains  more 
interesting  and  outspoken  matter  on  these  subjects  than  any  other 
ioumal. 

While  of  great  value  to  the  practitioner  for  therapeutic  sugges- 
tions of  a  practical,  up-to-date  and  definite  character,  its  editorials 
and  special  articles  are  what  make  The  Critic  and  Guide  unique 
among  journals,  read  eagerly  alike  by  the  medical  profession  and 
the  intelligent  laity. 


PUBLISHED  MONTHLY 
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